Erste Alpha-Version

ARCHIVE-FORMAT.txt

@@ -0,0 +1,54 @@
+MikeMail local archive, format 1
+
+Location: Application Support/MikeMail/Archive inside the macOS app sandbox.
+Mail.sqlite is the SwiftData index, with a versioned schema/migration plan.
+Objects/<SHA-256>.eml contains immutable original RFC 5322/MIME bytes, including
+all attachments. Paths are relative and content-addressed; user attachment
+filenames are never used as filesystem paths. Identical messages share an object.
+format.json identifies the archive format.
+
+Account settings, folder trees and recipient history are stored in the database.
+Existing UserDefaults settings migrate on first archive creation. Passwords stay
+in Keychain and are never included in snapshots. A restore to another Mac needs
+passwords entered again.
+
+Refresh inventories all selectable folders and compares UIDVALIDITY/UID/FLAGS.
+Only missing message bodies download. Removed messages and old UID generations
+are hidden from the current folder but retained in the archive. New bodies are
+staged before a complete inventory is reconciled. Failed downloads can resume.
+Offline folder selection performs no network access. Server-side read flags are
+stored; this change does not add local read/delete/move editing operations.
+Initial synchronization downloads all messages, subject to the transport's 40 MB
+per-message limit; failed folders are reported and remain incomplete.
+
+Future backup UI should call MailArchive.exportSnapshot(to:) after synchronization
+finishes, rather than copying the live SQLite file (which may have a WAL).
+The logical snapshot includes manifest.json with formatVersion, date, complete
+configuration, every message record (including hidden ones), and its EML objects.
+Export serializes with archive mutations, verifies SHA-256, writes a staging
+directory, then renames it. No absolute paths or credentials are exported.
+Unreferenced orphan objects from interrupted writes are not exported.
+
+MailArchive.restoreSnapshot(from:to:) validates version, unique record IDs, file
+references and hashes, then reconstructs a NEW database. It refuses an existing
+destination. A future restore UI must first stage/validate, stop all sync and
+close the current archive, then switch archives while retaining the previous one
+for rollback. Do not replace an open SQLite store. Restore is local only and
+does not upload or delete server mail.
+
+Backup/restore engine is implemented and tested; user-facing backup/restore
+buttons, scheduling, compression and encryption are intentionally not yet added.
+A backup contains only mail already downloaded, not inaccessible server mail.
+
+App icon: generated using built-in image_gen, resized with macOS sips.
+Asset: MikeMail/Assets.xcassets/AppIcon.appiconset/MikeMail-1024.png
+Generation prompt:
+Use case: stylized-concept. Asset: production macOS application icon for MikeMail,
+square 1024x1024. Create a beautiful premium blue 3D mail app icon: a sculpted
+pearly white envelope with crisp folded triangular flap, softly rounded edges,
+hovering subtly above a rich cobalt-to-azure blue rounded-square tile, depth and
+bevel, restrained luminous cyan rim highlights, soft studio reflections and
+ambient occlusion. Straight-on view, balanced centered composition, clear simple
+silhouette readable at 16px. Blue tile occupies about 88% of canvas, transparent
+outside rounded tile with soft small shadow. No text, letters, badges, watermark,
+extra objects or presentation mockup. Actual standalone icon artwork.

MikeMail.xcodeproj/project.xcproj

@@ -44,6 +44,7 @@
         "DEVELOPMENT_TEAM": "GQR972L9NJ",
         "ENABLE_APP_SANDBOX": "YES",
         "ENABLE_HARDENED_RUNTIME": "YES",
+        "ENABLE_OUTGOING_NETWORK_CONNECTIONS": "YES",
         "ENABLE_PREVIEWS": "YES",
         "ENABLE_USER_SELECTED_FILES": "readonly",
         "GENERATE_INFOPLIST_FILE": "YES",
@@ -53,6 +54,10 @@
           "@executable_path/../Frameworks",
         ],
         "MARKETING_VERSION": "1.0",
+        "OTHER_LDFLAGS": [
+          "$(inherited)",
+          "-lcurl",
+        ],
         "PRODUCT_BUNDLE_IDENTIFIER": "Dr.-med.-Michael-Ku-bler.MikeMail",
         "PRODUCT_NAME": "$(TARGET_NAME)",
         "REGISTER_APP_GROUPS": "YES",
@@ -60,6 +65,7 @@
         "SWIFT_APPROACHABLE_CONCURRENCY": "YES",
         "SWIFT_DEFAULT_ACTOR_ISOLATION": "MainActor",
         "SWIFT_EMIT_LOC_STRINGS": "YES",
+        "SWIFT_OBJC_BRIDGING_HEADER": "MikeMail/MailSMTP.h",
         "SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY": "YES",
         "SWIFT_VERSION": "5.0",
       },

MikeMail/AccountsView.swift

@@ -0,0 +1,126 @@
+import SwiftUI
+
+struct AccountsView: View {
+    let store: MailStore
+    @Environment(\.dismiss) private var dismiss
+    @State private var selection: UUID?
+    @State private var drafts: [UUID: MailAccount] = [:]
+    @State private var passwords: [UUID: String] = [:]
+    @State private var newAccount: MailAccount?
+    @State private var error: String?
+    @State private var confirmingDelete = false
+
+    var body: some View {
+        VStack(spacing: 0) {
+            HStack(spacing: 0) {
+                List(selection: $selection) {
+                    ForEach(store.accounts) { account in
+                        VStack(alignment: .leading) {
+                            Text(account.name.isEmpty ? account.email : account.name)
+                            Text(account.email).font(.caption).foregroundStyle(.secondary)
+                        }.tag(account.id)
+                    }
+                    if let newAccount {
+                        Label("Neues Konto", systemImage: "plus.circle").tag(newAccount.id)
+                    }
+                }
+                .frame(width: 230)
+                .accessibilityIdentifier("accountList")
+                Divider()
+                VStack(alignment: .leading, spacing: 18) {
+                    Text("Konteneinstellungen").font(.title2).bold()
+                    if let id = selection, let account = drafts[id] {
+                        AccountSettingsForm(account: Binding(
+                            get: { drafts[id] ?? account },
+                            set: { drafts[id] = $0 }
+                        ), password: Binding(
+                            get: { passwords[id] ?? "" },
+                            set: { passwords[id] = $0 }
+                        ))
+                        Text("Ein leeres Passwortfeld behält das gespeicherte Passwort bei. Änderungen mit „Speichern“ übernehmen.")
+                            .font(.caption).foregroundStyle(.secondary)
+                    } else {
+                        ContentUnavailableView("Kein Konto ausgewählt", systemImage: "person.crop.circle",
+                            description: Text("Füge ein Konto hinzu oder wähle links ein Konto aus."))
+                    }
+                    if let error { Text(error).foregroundStyle(.red) }
+                    Spacer()
+                    HStack {
+                        Spacer()
+                        Button("Speichern") { save() }
+                            .disabled(selection == nil)
+                            .keyboardShortcut(.defaultAction)
+                    }
+                }
+                .padding(24).frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .topLeading)
+            }
+            Divider()
+            HStack {
+                Button("Neues Konto hinzufügen", systemImage: "plus") {
+                    if let newAccount { selection = newAccount.id }
+                    else {
+                        let account = MailAccount()
+                        newAccount = account
+                        drafts[account.id] = account
+                        selection = account.id
+                    }
+                    error = nil
+                }
+                Button("Konto löschen", systemImage: "minus", role: .destructive) { confirmingDelete = true }
+                    .disabled(selection == nil || store.isBusy)
+                Spacer()
+                Button("Schließen") { dismiss() }.keyboardShortcut(.cancelAction)
+            }.padding(16)
+        }
+        .frame(width: 850, height: 480)
+        .onAppear {
+            drafts = Dictionary(uniqueKeysWithValues: store.accounts.map { ($0.id, $0) })
+            selection = store.accounts.first?.id
+        }
+        .onChange(of: selection) { _, _ in error = nil }
+        .confirmationDialog("Konto aus MikeMail entfernen?", isPresented: $confirmingDelete) {
+            Button("Konto löschen", role: .destructive) { delete() }
+            Button("Abbrechen", role: .cancel) {}
+        } message: {
+            Text("Die lokalen Kontoeinstellungen und das gespeicherte Passwort werden entfernt. Mails auf dem Server bleiben erhalten.")
+        }
+    }
+
+    private func save() {
+        guard let id = selection, let account = drafts[id] else { return }
+        do {
+            try store.save(account: account, password: passwords[id] ?? "")
+            passwords[id] = nil
+            if newAccount?.id == id { newAccount = nil }
+            error = nil
+        } catch { self.error = error.localizedDescription }
+    }
+
+    private func delete() {
+        guard let id = selection else { return }
+        do {
+            if newAccount?.id == id { newAccount = nil }
+            else { try store.deleteAccount(id: id) }
+            drafts[id] = nil
+            passwords[id] = nil
+            selection = store.accounts.first?.id ?? newAccount?.id
+        } catch { self.error = error.localizedDescription }
+    }
+}
+
+struct AccountSettingsForm: View {
+    @Binding var account: MailAccount
+    @Binding var password: String
+
+    var body: some View {
+        Form {
+            TextField("Name", text: $account.name)
+            TextField("E-Mail-Adresse", text: $account.email).accessibilityIdentifier("accountEmail")
+            TextField("Benutzername", text: $account.username)
+            TextField("Server", text: $account.host)
+            TextField("IMAP-Port (TLS)", value: $account.imapPort, format: .number.grouping(.never))
+            TextField("SMTP-Port (587 STARTTLS / 465 TLS)", value: $account.smtpPort, format: .number.grouping(.never))
+            SecureField("Passwort", text: $password)
+        }
+    }
+}

MikeMail/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -3,52 +3,62 @@
     {
       "idiom": "mac",
       "scale": "1x",
-      "size" : "16x16"
+      "size": "16x16",
+      "filename": "MikeMail-16.png"
     },
     {
       "idiom": "mac",
       "scale": "2x",
-      "size" : "16x16"
+      "size": "16x16",
+      "filename": "MikeMail-32.png"
     },
     {
       "idiom": "mac",
       "scale": "1x",
-      "size" : "32x32"
+      "size": "32x32",
+      "filename": "MikeMail-32.png"
     },
     {
       "idiom": "mac",
       "scale": "2x",
-      "size" : "32x32"
+      "size": "32x32",
+      "filename": "MikeMail-64.png"
     },
     {
       "idiom": "mac",
       "scale": "1x",
-      "size" : "128x128"
+      "size": "128x128",
+      "filename": "MikeMail-128.png"
     },
     {
       "idiom": "mac",
       "scale": "2x",
-      "size" : "128x128"
+      "size": "128x128",
+      "filename": "MikeMail-256.png"
     },
     {
       "idiom": "mac",
       "scale": "1x",
-      "size" : "256x256"
+      "size": "256x256",
+      "filename": "MikeMail-256.png"
     },
     {
       "idiom": "mac",
       "scale": "2x",
-      "size" : "256x256"
+      "size": "256x256",
+      "filename": "MikeMail-512.png"
     },
     {
       "idiom": "mac",
       "scale": "1x",
-      "size" : "512x512"
+      "size": "512x512",
+      "filename": "MikeMail-512.png"
     },
     {
       "idiom": "mac",
       "scale": "2x",
-      "size" : "512x512"
+      "size": "512x512",
+      "filename": "MikeMail-1024.png"
     }
   ],
   "info": {

MikeMail/ContentView.swift

@@ -1,59 +1,258 @@
-//
-//  ContentView.swift
-//  MikeMail
-//
-//  Created by Dr. med. Michael Kübler on 06.11.26.
-//
-
 import SwiftUI
-import SwiftData
+import UniformTypeIdentifiers
 
 struct ContentView: View {
-    @Environment(\.modelContext) private var modelContext
-    @Query private var items: [Item]
+    let store: MailStore
+    @State private var selectedFolder: String?
+    @State private var selectedMessage: String?
+    @State private var showingAccounts = false
+    @State private var composing = false
+    @State private var search = ""
 
     var body: some View {
         NavigationSplitView {
-            List {
-                ForEach(items) { item in
-                    NavigationLink {
-                        Text("Item at \(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))")
-                    } label: {
-                        Text(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))
-                    }
-                }
-                .onDelete(perform: deleteItems)
-            }
-            .navigationSplitViewColumnWidth(min: 180, ideal: 200)
-            .toolbar {
-                ToolbarItem {
-                    Button(action: addItem) {
-                        Label("Add Item", systemImage: "plus")
-                    }
-                }
-            }
+            AccountSidebar(accounts: store.accounts, folders: store.folders, selection: $selectedFolder)
+                .navigationSplitViewColumnWidth(min: 200, ideal: 250, max: 380)
         } detail: {
-            Text("Select an item")
+            VSplitView {
+                MessageTable(messages: store.messages.filter {
+                    search.isEmpty || $0.subject.localizedCaseInsensitiveContains(search) || $0.sender.localizedCaseInsensitiveContains(search)
+                }, selection: $selectedMessage)
+                .frame(minHeight: 160, idealHeight: 300)
+                MessageReader(message: store.messages.first { $0.id == selectedMessage })
+                    .frame(minHeight: 220, maxHeight: .infinity)
+            }
+            .safeAreaInset(edge: .bottom) {
+                HStack {
+                    if store.isBusy { ProgressView().controlSize(.small) }
+                    Text(store.status).font(.caption).foregroundStyle(.secondary)
+                    Spacer()
+                    if store.messages.count < store.totalMessages {
+                        Button("Weitere laden") {
+                            Task { await store.load(folderID: selectedFolder, more: true) }
+                        }.disabled(store.isBusy)
+                    }
+                    Text("\(store.messages.count) Nachrichten").font(.caption).foregroundStyle(.secondary)
+                }
+                .padding(8)
+                .background(.bar)
+            }
+        }
+        .navigationTitle("MikeMail")
+        .searchable(text: $search, prompt: "Absender oder Betreff suchen")
+        .toolbar {
+            ToolbarItemGroup {
+                Button("Abrufen", systemImage: "arrow.clockwise") {
+                    Task { await store.refresh(folderID: selectedFolder) }
+                }
+                .disabled(store.isBusy)
+                Button("Neue Nachricht", systemImage: "square.and.pencil") { composing = true }
+                    .keyboardShortcut("n", modifiers: .command)
+                    .disabled(store.accounts.isEmpty)
+                Button("Konten", systemImage: "person.crop.circle") { showingAccounts = true }
+            }
+        }
+        .sheet(isPresented: $showingAccounts) { AccountsView(store: store) }
+        .sheet(isPresented: $composing) { ComposeView(store: store) }
+        .alert("MikeMail", isPresented: Binding(get: { store.error != nil }, set: { if !$0 { store.error = nil } })) {
+            Button("OK") { store.error = nil }
+        } message: { Text(store.error ?? "") }
+        .onChange(of: selectedFolder) { _, folder in
+            selectedMessage = nil
+            Task { await store.load(folderID: folder) }
+        }
+        .frame(minWidth: 850, minHeight: 550)
     }
 }
 
-    private func addItem() {
-        withAnimation {
-            let newItem = Item(timestamp: Date())
-            modelContext.insert(newItem)
+struct AccountSidebar: View {
+    let accounts: [MailAccount]
+    let folders: [UUID: [MailFolder]]
+    @Binding var selection: String?
+
+    var body: some View {
+        List(selection: $selection) {
+            ForEach(accounts) { account in
+                DisclosureGroup {
+                    OutlineGroup(folders[account.id] ?? [], children: \.children) { folder in
+                        Label(folder.name, systemImage: folder.icon)
+                            .tag(folder.id)
+                            .selectionDisabled(!folder.selectable)
+                    }
+                    if folders[account.id] == nil {
+                        Text("Zum Laden „Abrufen“ wählen").font(.caption).foregroundStyle(.secondary)
+                            .selectionDisabled()
+                    }
+                } label: {
+                    VStack(alignment: .leading) {
+                        Label(account.name.isEmpty ? account.email : account.name, systemImage: "person.crop.circle")
+                        Text(account.email).font(.caption).foregroundStyle(.secondary)
+                    }
+                }
+            }
+        }
+        .listStyle(.sidebar)
     }
 }
 
-    private func deleteItems(offsets: IndexSet) {
-        withAnimation {
-            for index in offsets {
-                modelContext.delete(items[index])
+struct MessageTable: View {
+    let messages: [MailMessage]
+    @Binding var selection: String?
+    @State private var sortOrder = [KeyPathComparator(\MailMessage.date, order: .reverse)]
+
+    var body: some View {
+        Table(messages.sorted(using: sortOrder), selection: $selection, sortOrder: $sortOrder) {
+            TableColumn("Anhang") { message in
+                if !message.attachments.isEmpty {
+                    Image(systemName: "paperclip")
+                        .accessibilityLabel("\(message.attachments.count) Anhänge")
+                }
+            }.width(55)
+            TableColumn("Absender", value: \.sender).width(min: 110, ideal: 160)
+            TableColumn("Datum", value: \.date) { message in
+                if message.date == .distantPast { Text("—") }
+                else { Text(message.date, format: .dateTime.day().month().year().hour().minute()) }
+            }.width(min: 120, ideal: 150)
+            TableColumn("Betreff", value: \.subject).width(min: 160, ideal: 280)
+        }
+        .overlay {
+            if messages.isEmpty {
+                ContentUnavailableView("Keine Nachrichten", systemImage: "tray",
+                    description: Text("Wähle einen Ordner und rufe deine E-Mails ab."))
             }
         }
     }
 }
 
-#Preview {
-    ContentView()
-        .modelContainer(for: Item.self, inMemory: true)
+struct AttachmentDocument: FileDocument {
+    static var readableContentTypes: [UTType] { [.data] }
+    var data: Data
+    init(data: Data) { self.data = data }
+    init(configuration: ReadConfiguration) throws { data = configuration.file.regularFileContents ?? Data() }
+    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper { FileWrapper(regularFileWithContents: data) }
 }
+
+struct MessageReader: View {
+    let message: MailMessage?
+    @State private var exportDocument: AttachmentDocument?
+    @State private var exportName = "Anhang"
+    @State private var exporting = false
+    @State private var error: String?
+
+    var body: some View {
+        ScrollView {
+            if let message {
+                VStack(alignment: .leading, spacing: 16) {
+                    Text(message.subject).font(.title2).bold().textSelection(.enabled)
+                    VStack(alignment: .leading, spacing: 5) {
+                        Text("Von: \(message.sender)")
+                        Text("An: \(message.recipient)").foregroundStyle(.secondary)
+                        if message.date != .distantPast {
+                            Text(message.date, format: .dateTime.day().month(.wide).year().hour().minute()).foregroundStyle(.secondary)
+                        }
+                    }.textSelection(.enabled)
+                    if !message.attachments.isEmpty {
+                        ForEach(message.attachments) { attachment in
+                            Button {
+                                exportDocument = AttachmentDocument(data: attachment.data)
+                                exportName = (attachment.name as NSString).lastPathComponent
+                                exporting = true
+                            } label: {
+                                Label("\(attachment.name) · \(attachment.data.count.formatted(.byteCount(style: .file)))", systemImage: "paperclip")
+                            }
+                            .help("Anhang speichern")
+                        }
+                    }
+                    Divider()
+                    Text(message.body).textSelection(.enabled).frame(maxWidth: .infinity, alignment: .leading)
+                }
+                .padding(24)
+                .frame(maxWidth: .infinity, alignment: .leading)
+            } else {
+                ContentUnavailableView("Nachricht auswählen", systemImage: "envelope.open",
+                    description: Text("Der Inhalt und die Anhänge erscheinen hier."))
+                    .frame(maxWidth: .infinity, minHeight: 220)
+            }
+        }
+        .fileExporter(isPresented: $exporting, document: exportDocument, contentType: .data, defaultFilename: exportName) { result in
+            if case .failure(let failure) = result { error = failure.localizedDescription }
+        }
+        .alert("Anhang speichern", isPresented: Binding(get: { error != nil }, set: { if !$0 { error = nil } })) {
+            Button("OK") { error = nil }
+        } message: { Text(error ?? "") }
+    }
+}
+
+struct ComposeView: View {
+    let store: MailStore
+    @Environment(\.dismiss) private var dismiss
+    @State private var accountID: UUID?
+    @State private var recipient = ""
+    @State private var subject = ""
+    @State private var text = ""
+    @State private var attachments: [MailAttachment] = []
+    @State private var importing = false
+    @State private var sending = false
+    @State private var error: String?
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 14) {
+            Text("Neue Nachricht").font(.title2).bold()
+            Form {
+                Picker("Von", selection: $accountID) {
+                    ForEach(store.accounts) { account in Text(account.email).tag(Optional(account.id)) }
+                }
+                RecipientField(recipient: $recipient, history: store.recipientHistory)
+                TextField("Betreff", text: $subject)
+            }
+            TextEditor(text: $text).font(.body).frame(minHeight: 230).border(.quaternary)
+            ForEach(attachments) { attachment in
+                HStack {
+                    Label(attachment.name, systemImage: "paperclip")
+                    Spacer()
+                    Button("Entfernen", systemImage: "xmark.circle") { attachments.removeAll { $0.id == attachment.id } }
+                        .labelStyle(.iconOnly)
+                }
+            }
+            if let error { Text(error).foregroundStyle(.red).textSelection(.enabled) }
+            HStack {
+                Button("Abbrechen") { dismiss() }.keyboardShortcut(.cancelAction)
+                Button("Anhang hinzufügen", systemImage: "paperclip") { importing = true }
+                Spacer()
+                if sending { ProgressView().controlSize(.small) }
+                Button("Senden", systemImage: "paperplane") {
+                    sending = true
+                    error = nil
+                    Task {
+                        do {
+                            try await store.send(accountID: accountID, recipients: recipient, subject: subject, body: text, attachments: attachments)
+                            dismiss()
+                        } catch { self.error = error.localizedDescription }
+                        sending = false
+                    }
+                }
+                .buttonStyle(.borderedProminent)
+                .disabled(recipient.trimmingCharacters(in: .whitespaces).isEmpty || accountID == nil)
+            }
+        }
+        .padding(24).frame(width: 680, height: 620)
+        .disabled(sending)
+        .interactiveDismissDisabled(sending)
+        .onAppear { accountID = store.accounts.first?.id }
+        .fileImporter(isPresented: $importing, allowedContentTypes: [.data], allowsMultipleSelection: true) { result in
+            do {
+                for url in try result.get() {
+                    let access = url.startAccessingSecurityScopedResource()
+                    defer { if access { url.stopAccessingSecurityScopedResource() } }
+                    let size = try url.resourceValues(forKeys: [.fileSizeKey]).fileSize ?? 0
+                    guard size + attachments.reduce(0, { $0 + $1.data.count }) <= 20_000_000 else {
+                        throw MailError.message("Anhänge dürfen zusammen höchstens 20 MB groß sein.")
+                    }
+                    attachments.append(MailAttachment(name: url.lastPathComponent, mimeType: "application/octet-stream", data: try Data(contentsOf: url)))
+                }
+            } catch { self.error = error.localizedDescription }
+        }
+    }
+}
+
+#Preview { ContentView(store: MailStore()) }

MikeMail/IMAPClient.swift

@@ -0,0 +1,209 @@
+import Foundation
+
+@MainActor
+final class IMAPClient {
+    private let connection: TLSConnection
+    private var sequence = 0
+
+    init(account: MailAccount) throws {
+        connection = try TLSConnection(host: account.host, port: account.imapPort)
+    }
+
+    func close() { connection.close() }
+
+    func login(account: MailAccount, password: String) async throws {
+        try await connection.open()
+        let greeting = try await connection.readLine()
+        if greeting.uppercased().hasPrefix("* PREAUTH") { return }
+        guard greeting.uppercased().hasPrefix("* OK") else { throw MailError.message("IMAP: \(greeting)") }
+        _ = try await command("LOGIN \(Self.quote(account.username)) \(Self.quote(password))")
+    }
+
+    static func quote(_ value: String) throws -> String {
+        guard !value.unicodeScalars.contains(where: { CharacterSet.controlCharacters.contains($0) }) else {
+            throw MailError.message("Ungültiges Steuerzeichen in IMAP-Eingabe.")
+        }
+        return "\"" + value.replacingOccurrences(of: "\\", with: "\\\\").replacingOccurrences(of: "\"", with: "\\\"") + "\""
+    }
+
+    struct Response {
+        var lines: [String] = []
+        var literals: [Data] = []
+    }
+
+    private func command(_ value: String) async throws -> Response {
+        sequence += 1
+        let tag = "M\(sequence)"
+        try await connection.line("\(tag) \(value)")
+        return try await response(tag: tag)
+    }
+
+    private func response(tag: String) async throws -> Response {
+        var result = Response()
+        for _ in 0..<100_000 {
+            let line = try await connection.readLine()
+            if line.hasPrefix(tag + " ") {
+                guard line.uppercased().hasPrefix(tag + " OK") else {
+                    throw MailError.message("IMAP: \(line)")
+                }
+                return result
+            }
+            if line.uppercased().hasPrefix("* BYE") { throw MailError.message("IMAP: Verbindung vom Server beendet.") }
+            result.lines.append(line)
+            if line.hasSuffix("}"), let start = line.lastIndex(of: "{"),
+               let count = Int(line[line.index(after: start)..<line.index(before: line.endIndex)]) {
+                result.literals.append(try await connection.readBytes(count))
+            }
+        }
+        throw MailError.message("IMAP-Antwort überschreitet das Limit.")
+    }
+
+    func folders(accountID: UUID) async throws -> [MailFolder] {
+        let result = try await command("LIST \"\" \"*\"")
+        var entries: [(path: String, delimiter: String, selectable: Bool)] = []
+        var literalIndex = 0
+        for line in result.lines where line.uppercased().hasPrefix("* LIST ") {
+            guard let close = line.firstIndex(of: ")") else { continue }
+            let flags = line[..<close].lowercased()
+            let rest = String(line[line.index(after: close)...])
+            let tokens = Self.tokens(rest)
+            guard tokens.count >= 2 else { continue }
+            var path = tokens[1]
+            if path.hasPrefix("{"), literalIndex < result.literals.count {
+                path = String(decoding: result.literals[literalIndex], as: UTF8.self)
+                literalIndex += 1
+            }
+            entries.append((path, tokens[0].uppercased() == "NIL" ? "" : tokens[0], !flags.contains("\\noselect")))
+        }
+        func build(prefix: String?, entries: [(path: String, delimiter: String, selectable: Bool)]) -> [MailFolder] {
+            var roots: [String: MailFolder] = [:]
+            for entry in entries {
+                let remainder: String
+                if let prefix {
+                    let start = prefix + entry.delimiter
+                    guard !entry.delimiter.isEmpty, entry.path.hasPrefix(start) else { continue }
+                    remainder = String(entry.path.dropFirst(start.count))
+                } else { remainder = entry.path }
+                let component = entry.delimiter.isEmpty ? remainder : remainder.components(separatedBy: entry.delimiter)[0]
+                let path = prefix.map { $0 + entry.delimiter + component } ?? component
+                let exact = entries.first { $0.path == path }
+                roots[path] = MailFolder(accountID: accountID, path: path,
+                    name: path.uppercased() == "INBOX" ? "Posteingang" : Self.decodeMailbox(component),
+                    selectable: exact?.selectable ?? false)
+            }
+            return roots.values.map { folder in
+                var folder = folder
+                let descendants = build(prefix: folder.path, entries: entries)
+                folder.children = descendants.isEmpty ? nil : descendants
+                return folder
+            }.sorted {
+                if $0.path.uppercased() == "INBOX" { return true }
+                if $1.path.uppercased() == "INBOX" { return false }
+                return $0.name.localizedStandardCompare($1.name) == .orderedAscending
+            }
+        }
+        return build(prefix: nil, entries: entries)
+    }
+
+    /// IMAP quoted strings may contain escaped quotes or spaces.
+    static func tokens(_ value: String) -> [String] {
+        var tokens: [String] = []
+        var token = ""
+        var quoted = false
+        var escaped = false
+        var started = false
+        for character in value {
+            if escaped { token.append(character); escaped = false; continue }
+            if quoted && character == "\\" { escaped = true; continue }
+            if character == "\"" { quoted.toggle(); started = true; continue }
+            if character.isWhitespace && !quoted {
+                if started { tokens.append(token); token = ""; started = false }
+            } else { token.append(character); started = true }
+        }
+        if started { tokens.append(token) }
+        return tokens
+    }
+
+    static func decodeMailbox(_ value: String) -> String {
+        var result = ""
+        var remainder = value[...]
+        while let start = remainder.firstIndex(of: "&") {
+            result += remainder[..<start]
+            guard let end = remainder[start...].firstIndex(of: "-") else { result += remainder[start...]; return result }
+            var encoded = String(remainder[remainder.index(after: start)..<end])
+            if encoded.isEmpty { result += "&" }
+            else {
+                encoded = encoded.replacingOccurrences(of: ",", with: "/")
+                while encoded.count % 4 != 0 { encoded += "=" }
+                if let data = Data(base64Encoded: encoded), let decoded = String(data: data, encoding: .utf16BigEndian) { result += decoded }
+                else { result += remainder[start...end] }
+            }
+            remainder = remainder[remainder.index(after: end)...]
+        }
+        return result + remainder
+    }
+
+    static func uidValidity(from lines: [String]) throws -> String {
+        for line in lines {
+            guard let start = line.range(of: "[UIDVALIDITY ", options: .caseInsensitive),
+                  let end = line[start.upperBound...].firstIndex(of: "]") else { continue }
+            let value = String(line[start.upperBound..<end])
+            if let number = UInt64(value), number > 0 { return value }
+        }
+        throw MailError.message("IMAP-Server liefert keine gültige UIDVALIDITY; Abgleich abgebrochen.")
+    }
+
+    static func parseFlags(_ lines: [String]) throws -> [UInt64: [String]] {
+        let uidPattern = try NSRegularExpression(pattern: "(?i)\\bUID ([0-9]+)")
+        let flagsPattern = try NSRegularExpression(pattern: "(?i)\\bFLAGS \\(([^)]*)\\)")
+        var result: [UInt64: [String]] = [:]
+        for line in lines {
+            let range = NSRange(line.startIndex..., in: line)
+            guard let uidMatch = uidPattern.firstMatch(in: line, range: range),
+                  let uidRange = Range(uidMatch.range(at: 1), in: line),
+                  let uid = UInt64(line[uidRange]),
+                  let flagsMatch = flagsPattern.firstMatch(in: line, range: range),
+                  let flagsRange = Range(flagsMatch.range(at: 1), in: line) else { continue }
+            result[uid] = line[flagsRange].split(separator: " ").map(String.init)
+        }
+        return result
+    }
+
+    func inventory(folder: MailFolder) async throws -> MailboxInventory {
+        let examined = try await command("EXAMINE \(Self.quote(folder.path))")
+        let validity = try Self.uidValidity(from: examined.lines)
+        let search = try await command("UID SEARCH ALL")
+        guard let line = search.lines.first(where: { $0.uppercased().hasPrefix("* SEARCH") }) else {
+            throw MailError.message("Unvollständige IMAP-Bestandsliste.")
+        }
+        let ids = line.split(separator: " ").dropFirst(2).compactMap { UInt64($0) }
+        var flags: [UInt64: [String]] = [:]
+        for start in stride(from: 0, to: ids.count, by: 200) {
+            let batch = ids[start..<min(start + 200, ids.count)].map(String.init).joined(separator: ",")
+            let fetched = try await command("UID FETCH \(batch) (UID FLAGS)")
+            flags.merge(try Self.parseFlags(fetched.lines)) { _, new in new }
+        }
+        guard Set(flags.keys) == Set(ids) else {
+            throw MailError.message("Der Ordner hat sich während des Abgleichs verändert. Bitte erneut abrufen.")
+        }
+        return MailboxInventory(validity: validity, flags: flags)
+    }
+
+    func rawMessage(uid: UInt64) async throws -> Data {
+        let fetched = try await command("UID FETCH \(uid) (UID BODY.PEEK[])")
+        guard let raw = fetched.literals.first else {
+            throw MailError.message("Nachricht \(uid) ist nicht mehr verfügbar; bitte erneut abrufen.")
+        }
+        return raw
+    }
+
+    func appendSent(_ message: Data, path: String) async throws {
+        sequence += 1
+        let tag = "M\(sequence)"
+        try await connection.line("\(tag) APPEND \(Self.quote(path)) (\\Seen) {\(message.count)}")
+        let ready = try await connection.readLine()
+        guard ready.hasPrefix("+") else { throw MailError.message("Gesendet-Kopie konnte nicht gespeichert werden: \(ready)") }
+        try await connection.send(message + Data("\r\n".utf8))
+        _ = try await response(tag: tag)
+    }
+}

MikeMail/MIME.swift

@@ -0,0 +1,175 @@
+import Foundation
+
+/// MIME decoding keeps arbitrary attachment bytes separate from decoded text.
+enum MIME {
+    static func headers(_ text: String) -> [String: String] {
+        let unfolded = text.replacingOccurrences(of: "\r\n", with: "\n")
+            .replacingOccurrences(of: "\n[ \t]+", with: " ", options: .regularExpression)
+        var result: [String: String] = [:]
+        for line in unfolded.components(separatedBy: "\n") {
+            guard let colon = line.firstIndex(of: ":") else { continue }
+            result[String(line[..<colon]).lowercased()] = String(line[line.index(after: colon)...]).trimmingCharacters(in: .whitespaces)
+        }
+        return result
+    }
+
+    static func split(_ data: Data) -> ([String: String], Data) {
+        for separator in [Data("\r\n\r\n".utf8), Data("\n\n".utf8)] {
+            if let range = data.range(of: separator) {
+                return (headers(String(decoding: data[..<range.lowerBound], as: UTF8.self)), Data(data[range.upperBound...]))
+            }
+        }
+        return ([:], data)
+    }
+
+    static func parameter(_ name: String, in value: String) -> String? {
+        let pattern = "(?:^|;)\\s*" + NSRegularExpression.escapedPattern(for: name) + "=\\s*(?:\"([^\"]*)\"|([^;\\s]+))"
+        guard let regex = try? NSRegularExpression(pattern: pattern, options: .caseInsensitive),
+              let match = regex.firstMatch(in: value, range: NSRange(value.startIndex..., in: value)) else { return nil }
+        for i in 1...2 {
+            if let range = Range(match.range(at: i), in: value) { return String(value[range]) }
+        }
+        return nil
+    }
+
+    static func quotedPrintable(_ data: Data, header: Bool = false) -> Data {
+        let bytes = Array(data)
+        var output = Data()
+        var i = 0
+        while i < bytes.count {
+            if bytes[i] == 61 {
+                if i + 2 < bytes.count, bytes[i + 1] == 13, bytes[i + 2] == 10 { i += 3; continue }
+                if i + 1 < bytes.count, bytes[i + 1] == 10 { i += 2; continue }
+                if i + 2 < bytes.count, let value = UInt8(String(decoding: bytes[(i + 1)...(i + 2)], as: UTF8.self), radix: 16) {
+                    output.append(value); i += 3; continue
+                }
+            }
+            output.append(header && bytes[i] == 95 ? 32 : bytes[i])
+            i += 1
+        }
+        return output
+    }
+
+    static func text(_ data: Data, charset: String?) -> String {
+        let encoding: String.Encoding = switch charset?.lowercased() {
+        case "iso-8859-1", "latin1": .isoLatin1
+        case "windows-1252": .windowsCP1252
+        case "us-ascii": .ascii
+        default: .utf8
+        }
+        return String(data: data, encoding: encoding) ?? String(data: data, encoding: .isoLatin1) ?? ""
+    }
+
+    static func decodeHeader(_ value: String) -> String {
+        guard let regex = try? NSRegularExpression(pattern: "=\\?([^?]+)\\?([bBqQ])\\?([^?]*)\\?=") else { return value }
+        // Whitespace between adjacent encoded words is folding, not displayed content.
+        let source = value.replacingOccurrences(of: "(?<=\\?=)\\s+(?==\\?)", with: "", options: .regularExpression)
+        var result = source
+        for match in regex.matches(in: source, range: NSRange(source.startIndex..., in: source)).reversed() {
+            guard let whole = Range(match.range, in: result),
+                  let cs = Range(match.range(at: 1), in: source),
+                  let enc = Range(match.range(at: 2), in: source),
+                  let content = Range(match.range(at: 3), in: source) else { continue }
+            let raw = String(source[content])
+            let bytes = source[enc].lowercased() == "b" ? Data(base64Encoded: raw) : quotedPrintable(Data(raw.utf8), header: true)
+            if let bytes { result.replaceSubrange(whole, with: text(bytes, charset: String(source[cs]))) }
+        }
+        return result
+    }
+
+    static func parse(_ data: Data, id: String) -> MailMessage {
+        let (fields, _) = split(data)
+        var bodies: [String] = []
+        var htmlBodies: [String] = []
+        var attachments: [MailAttachment] = []
+        parsePart(data, depth: 0, bodies: &bodies, htmlBodies: &htmlBodies, attachments: &attachments)
+        let dateFormatter = DateFormatter()
+        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+        var date: Date?
+        for format in ["EEE, d MMM yyyy HH:mm:ss Z", "d MMM yyyy HH:mm:ss Z", "EEE, d MMM yyyy HH:mm Z"] {
+            dateFormatter.dateFormat = format
+            date = dateFormatter.date(from: fields["date"] ?? "")
+            if date != nil { break }
+        }
+        return MailMessage(id: id, sender: decodeHeader(fields["from"] ?? ""),
+            recipient: decodeHeader(fields["to"] ?? ""), subject: decodeHeader(fields["subject"] ?? "(Ohne Betreff)"),
+            date: date ?? .distantPast, body: bodies.isEmpty ? htmlBodies.joined(separator: "\n") : bodies.joined(separator: "\n"),
+            attachments: attachments)
+    }
+
+    private static func parsePart(_ data: Data, depth: Int, bodies: inout [String], htmlBodies: inout [String], attachments: inout [MailAttachment]) {
+        guard depth < 30 else { return }
+        let (fields, body) = split(data)
+        let type = fields["content-type"] ?? "text/plain"
+        if type.lowercased().hasPrefix("multipart/"), let boundary = parameter("boundary", in: type) {
+            // Boundaries are ASCII; Latin-1 preserves every byte through splitting.
+            let raw = String(data: body, encoding: .isoLatin1) ?? ""
+            let delimiter = "--" + boundary
+            let parts = raw.components(separatedBy: delimiter)
+            for part in parts.dropFirst() {
+                if part.hasPrefix("--") { break }
+                var part = part
+                // CRLF is one Swift Character, though it contains two bytes.
+                if part.hasPrefix("\r\n") || part.hasPrefix("\n") { part.removeFirst() }
+                if part.hasSuffix("\r\n") || part.hasSuffix("\n") { part.removeLast() }
+                if let bytes = part.data(using: .isoLatin1) {
+                    parsePart(bytes, depth: depth + 1, bodies: &bodies, htmlBodies: &htmlBodies, attachments: &attachments)
+                }
+            }
+            return
+        }
+        let transfer = fields["content-transfer-encoding"]?.lowercased() ?? ""
+        let decoded: Data
+        if transfer == "base64" { decoded = Data(base64Encoded: body, options: .ignoreUnknownCharacters) ?? Data() }
+        else if transfer == "quoted-printable" { decoded = quotedPrintable(body) }
+        else { decoded = body }
+        let disposition = fields["content-disposition"] ?? ""
+        let extendedName = parameter("filename*", in: disposition).flatMap { $0.components(separatedBy: "''").last?.removingPercentEncoding }
+        let name = extendedName ?? parameter("filename", in: disposition) ?? parameter("name", in: type)
+        if name != nil || disposition.lowercased().hasPrefix("attachment") || !type.lowercased().hasPrefix("text/") {
+            attachments.append(MailAttachment(name: decodeHeader(name ?? "Anhang"), mimeType: type.components(separatedBy: ";")[0], data: decoded))
+        } else {
+            let value = text(decoded, charset: parameter("charset", in: type))
+            if type.lowercased().hasPrefix("text/html") {
+                // Render HTML as text: remote images and active content are never loaded.
+                let plain = value.replacingOccurrences(of: "(?is)<(script|style)[^>]*>.*?</\\1>", with: "", options: .regularExpression)
+                    .replacingOccurrences(of: "(?i)<br\\s*/?>|</p>|</div>", with: "\n", options: .regularExpression)
+                    .replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression)
+                    .replacingOccurrences(of: "&nbsp;", with: " ").replacingOccurrences(of: "&lt;", with: "<")
+                    .replacingOccurrences(of: "&gt;", with: ">").replacingOccurrences(of: "&amp;", with: "&")
+                htmlBodies.append(plain)
+            } else { bodies.append(value) }
+        }
+    }
+
+    static func validAddress(_ value: String) -> Bool {
+        value.range(of: "^[A-Za-z0-9.!#$%&'*+/=?^_`{|}~-]+@[A-Za-z0-9](?:[A-Za-z0-9.-]*[A-Za-z0-9])?$", options: .regularExpression) != nil
+    }
+
+    static func compose(from: String, to: [String], subject: String, body: String, attachments: [MailAttachment]) throws -> Data {
+        guard validAddress(from), !to.isEmpty, to.allSatisfy(validAddress),
+              !subject.unicodeScalars.contains(where: { CharacterSet.newlines.contains($0) }) else {
+            throw MailError.message("Bitte gültige E-Mail-Adressen und einen einzeiligen Betreff eingeben.")
+        }
+        let boundary = "MikeMail-" + UUID().uuidString
+        let dateFormatter = DateFormatter()
+        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+        dateFormatter.dateFormat = "EEE, dd MMM yyyy HH:mm:ss Z"
+        func base64(_ data: Data) -> String {
+            data.base64EncodedString(options: [.lineLength76Characters, .endLineWithCarriageReturn, .endLineWithLineFeed])
+        }
+        var result = "From: \(from)\r\nTo: \(to.joined(separator: ", "))\r\n"
+        result += "Subject: =?UTF-8?B?\(Data(subject.utf8).base64EncodedString())?=\r\n"
+        result += "Date: \(dateFormatter.string(from: Date()))\r\nMessage-ID: <\(UUID().uuidString)@mikemail.local>\r\n"
+        result += "MIME-Version: 1.0\r\nContent-Type: multipart/mixed; boundary=\"\(boundary)\"\r\n\r\n"
+        result += "--\(boundary)\r\nContent-Type: text/plain; charset=utf-8\r\nContent-Transfer-Encoding: base64\r\n\r\n\(base64(Data(body.utf8)))\r\n"
+        for attachment in attachments {
+            let safeName = attachment.name.addingPercentEncoding(withAllowedCharacters: .alphanumerics) ?? "Anhang"
+            result += "--\(boundary)\r\nContent-Type: application/octet-stream\r\n"
+            result += "Content-Disposition: attachment; filename*=UTF-8''\(safeName)\r\nContent-Transfer-Encoding: base64\r\n\r\n"
+            result += base64(attachment.data) + "\r\n"
+        }
+        result += "--\(boundary)--\r\n"
+        return Data(result.utf8)
+    }
+}

MikeMail/MailArchive.swift

@@ -0,0 +1,237 @@
+import Foundation
+import SwiftData
+import CryptoKit
+
+enum MailArchiveSchema: VersionedSchema {
+    static var versionIdentifier = Schema.Version(1, 0, 0)
+    static var models: [any PersistentModel.Type] { [ArchiveState.self, ArchivedMail.self] }
+
+    @Model final class ArchiveState {
+        @Attribute(.unique) var key: String
+        var payload: Data
+        init(key: String, payload: Data) { self.key = key; self.payload = payload }
+    }
+
+    @Model final class ArchivedMail {
+        @Attribute(.unique) var key: String
+        var folderID: String
+        var validity: String
+        var uid: String
+        var objectHash: String
+        var flags: [String]
+        var present: Bool
+        init(key: String, folderID: String, validity: String, uid: String, objectHash: String, flags: [String], present: Bool = true) {
+            self.key = key
+            self.folderID = folderID
+            self.validity = validity
+            self.uid = uid
+            self.objectHash = objectHash
+            self.flags = flags
+            self.present = present
+        }
+    }
+}
+
+enum MailArchiveMigration: SchemaMigrationPlan {
+    static var schemas: [any VersionedSchema.Type] { [MailArchiveSchema.self] }
+    static var stages: [MigrationStage] { [] }
+}
+
+struct ArchiveConfiguration: Codable {
+    var accounts: [MailAccount]
+    var folders: [UUID: [MailFolder]]
+    var recipients: [String]
+}
+
+struct MailboxInventory {
+    let validity: String
+    let flags: [UInt64: [String]]
+}
+
+struct ArchiveMailRecord: Codable {
+    let key: String
+    let folderID: String
+    let validity: String
+    let uid: String
+    let objectHash: String
+    let flags: [String]
+    let present: Bool
+}
+
+/// All mutations and snapshot creation run serially on the main actor without suspension.
+/// Immutable, content-addressed EML objects are written before their database references.
+@MainActor
+final class MailArchive {
+    nonisolated static var defaultRoot: URL {
+        URL.applicationSupportDirectory.appending(path: "MikeMail/Archive", directoryHint: .isDirectory)
+    }
+    let root: URL
+    private let container: ModelContainer
+    private let context: ModelContext
+
+    init(root: URL = MailArchive.defaultRoot) throws {
+        self.root = root
+        try FileManager.default.createDirectory(at: root.appending(path: "Objects"), withIntermediateDirectories: true)
+        let marker = root.appending(path: "format.json")
+        if FileManager.default.fileExists(atPath: marker.path) {
+            let version = try JSONDecoder().decode(Int.self, from: Data(contentsOf: marker))
+            guard version == 1 else { throw MailError.message("Nicht unterstützte Mailarchiv-Version: \(version).") }
+        }
+        let schema = Schema(versionedSchema: MailArchiveSchema.self)
+        let configuration = ModelConfiguration("MailArchive", schema: schema,
+            url: root.appending(path: "Mail.sqlite"), cloudKitDatabase: .none)
+        container = try ModelContainer(for: schema, migrationPlan: MailArchiveMigration.self, configurations: [configuration])
+        context = ModelContext(container)
+        context.autosaveEnabled = false
+        if !FileManager.default.fileExists(atPath: marker.path) { try Data("1".utf8).write(to: marker, options: .atomic) }
+    }
+
+    func configuration() throws -> ArchiveConfiguration? {
+        let key = "configuration"
+        let descriptor = FetchDescriptor<MailArchiveSchema.ArchiveState>(predicate: #Predicate { $0.key == key })
+        guard let state = try context.fetch(descriptor).first else { return nil }
+        return try JSONDecoder().decode(ArchiveConfiguration.self, from: state.payload)
+    }
+
+    func saveConfiguration(_ value: ArchiveConfiguration) throws {
+        let payload = try JSONEncoder().encode(value)
+        let key = "configuration"
+        do {
+            if let state = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchiveState>(predicate: #Predicate { $0.key == key })).first {
+                state.payload = payload
+            } else { context.insert(MailArchiveSchema.ArchiveState(key: key, payload: payload)) }
+            try context.save()
+        } catch { context.rollback(); throw error }
+    }
+
+    private func rows(folderID: String) throws -> [MailArchiveSchema.ArchivedMail] {
+        try context.fetch(FetchDescriptor(predicate: #Predicate<MailArchiveSchema.ArchivedMail> { $0.folderID == folderID }))
+    }
+
+    func knownUIDs(folderID: String, validity: String) throws -> Set<UInt64> {
+        Set(try rows(folderID: folderID).filter {
+            $0.validity == validity && FileManager.default.fileExists(atPath: objectURL($0.objectHash).path)
+        }.compactMap { UInt64($0.uid) })
+    }
+
+    func store(raw: Data, folderID: String, validity: String, uid: String, flags: [String], visible: Bool = true) throws {
+        let hash = Self.digest(raw)
+        let url = objectURL(hash)
+        if !FileManager.default.fileExists(atPath: url.path) { try raw.write(to: url, options: .atomic) }
+        let key = folderID + ":" + validity + ":" + uid
+        do {
+            if let row = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchivedMail>(predicate: #Predicate { $0.key == key })).first {
+                row.objectHash = hash
+                row.flags = flags
+                row.present = visible
+            } else {
+                context.insert(MailArchiveSchema.ArchivedMail(key: key, folderID: folderID, validity: validity,
+                    uid: uid, objectHash: hash, flags: flags, present: visible))
+            }
+            try context.save()
+        } catch { context.rollback(); throw error }
+    }
+
+    /// Reconcile only after a complete server inventory. Keep removed objects for future backups.
+    func reconcile(folderID: String, inventory: MailboxInventory) throws {
+        do {
+            for row in try rows(folderID: folderID) {
+                let flags = UInt64(row.uid).flatMap { inventory.flags[$0] }
+                row.present = row.validity == inventory.validity && flags != nil
+                if let flags, row.present { row.flags = flags }
+            }
+            try context.save()
+        } catch { context.rollback(); throw error }
+    }
+
+    func messages(folderID: String) throws -> [MailMessage] {
+        try rows(folderID: folderID).filter(\.present).map { row in
+            var mail = MIME.parse(try Data(contentsOf: objectURL(row.objectHash)), id: row.key)
+            mail.isRead = row.flags.contains { $0.lowercased() == "\\seen" }
+            return mail
+        }.sorted { $0.date > $1.date }
+    }
+
+    private func objectURL(_ hash: String) -> URL { root.appending(path: "Objects/\(hash).eml") }
+
+    static func digest(_ data: Data) -> String {
+        SHA256.hash(data: data).map { String(format: "%02x", $0) }.joined()
+    }
+
+    struct Snapshot: Codable {
+        let formatVersion: Int
+        let createdAt: Date
+        let configuration: ArchiveConfiguration
+        let messages: [ArchiveMailRecord]
+    }
+
+    /// Logical snapshot: never copy a live SQLite database without its WAL.
+    /// The manifest and immutable EML files are sufficient to rebuild the database on restore.
+    func exportSnapshot(to destination: URL) throws {
+        guard !FileManager.default.fileExists(atPath: destination.path) else {
+            throw MailError.message("Das Backup-Ziel existiert bereits.")
+        }
+        guard let configuration = try configuration() else { throw MailError.message("Archiv ist noch nicht eingerichtet.") }
+        try context.save()
+        let rows = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchivedMail>())
+        let records = rows.map { ArchiveMailRecord(key: $0.key, folderID: $0.folderID, validity: $0.validity,
+            uid: $0.uid, objectHash: $0.objectHash, flags: $0.flags, present: $0.present) }
+        let staging = destination.deletingLastPathComponent().appending(path: ".MikeMail-\(UUID().uuidString)")
+        do {
+            try FileManager.default.createDirectory(at: staging.appending(path: "Objects"), withIntermediateDirectories: true)
+            for hash in Set(records.map(\.objectHash)) {
+                let data = try Data(contentsOf: objectURL(hash))
+                guard Self.digest(data) == hash else { throw MailError.message("Beschädigte Archivdatei: \(hash)") }
+                try data.write(to: staging.appending(path: "Objects/\(hash).eml"), options: .atomic)
+            }
+            let snapshot = Snapshot(formatVersion: 1, createdAt: Date(), configuration: configuration, messages: records)
+            try JSONEncoder().encode(snapshot).write(to: staging.appending(path: "manifest.json"), options: .atomic)
+            try FileManager.default.moveItem(at: staging, to: destination)
+        } catch {
+            try? FileManager.default.removeItem(at: staging)
+            throw error
+        }
+    }
+
+    /// Restore into a NEW archive only. The live archive is never overwritten.
+    static func restoreSnapshot(from source: URL, to destination: URL) throws -> MailArchive {
+        guard !FileManager.default.fileExists(atPath: destination.path) else {
+            throw MailError.message("Wiederherstellung benötigt ein neues, leeres Zielverzeichnis.")
+        }
+        let snapshot = try JSONDecoder().decode(Snapshot.self, from: Data(contentsOf: source.appending(path: "manifest.json")))
+        guard snapshot.formatVersion == 1 else { throw MailError.message("Nicht unterstütztes Backup-Format.") }
+        guard Set(snapshot.messages.map(\.key)).count == snapshot.messages.count else {
+            throw MailError.message("Das Backup enthält doppelte Nachrichtenschlüssel.")
+        }
+        // Validate every referenced object before creating the destination.
+        for hash in Set(snapshot.messages.map(\.objectHash)) {
+            guard hash.count == 64, hash.allSatisfy({ $0.isHexDigit && !$0.isUppercase }) else {
+                throw MailError.message("Ungültiger Dateiverweis im Backup.")
+            }
+            let url = source.appending(path: "Objects/\(hash).eml")
+            guard try url.resourceValues(forKeys: [.isSymbolicLinkKey]).isSymbolicLink != true,
+                  digest(try Data(contentsOf: url)) == hash else {
+                throw MailError.message("Backup ist unvollständig oder beschädigt.")
+            }
+        }
+        let archive = try MailArchive(root: destination)
+        do {
+            try archive.saveConfiguration(snapshot.configuration)
+            for record in snapshot.messages {
+                let data = try Data(contentsOf: source.appending(path: "Objects/\(record.objectHash).eml"))
+                guard digest(data) == record.objectHash else { throw MailError.message("Backup wurde während des Restores verändert.") }
+                try data.write(to: archive.objectURL(record.objectHash), options: .atomic)
+                archive.context.insert(MailArchiveSchema.ArchivedMail(key: record.key, folderID: record.folderID,
+                    validity: record.validity, uid: record.uid, objectHash: record.objectHash,
+                    flags: record.flags, present: record.present))
+            }
+            try archive.context.save()
+            return archive
+        } catch {
+            archive.context.rollback()
+            // Destination is a newly created, failed restore; source and live archive are untouched.
+            try? FileManager.default.removeItem(at: destination)
+            throw error
+        }
+    }
+}

MikeMail/MailModels.swift

@@ -0,0 +1,101 @@
+import Foundation
+import Security
+
+struct MailAccount: Identifiable, Codable, Hashable, Sendable {
+    var id = UUID()
+    var name = ""
+    var email = ""
+    var username = ""
+    var host = ""
+    var smtpPort: UInt16 = 587
+    var imapPort: UInt16 = 993
+
+    static let testAccount = MailAccount(name: "Testkonto", email: "test@kuebler-sulzbach.de",
+        username: "test@kuebler-sulzbach.de", host: "w0099985.kasserver.com")
+}
+
+struct MailFolder: Identifiable, Hashable, Codable, Sendable {
+    var id: String { accountID.uuidString + ":" + path }
+    let accountID: UUID
+    let path: String
+    let name: String
+    var selectable = true
+    var children: [MailFolder]?
+
+    var icon: String {
+        switch path.lowercased() {
+        case "inbox": "tray"
+        case let value where value.contains("sent"): "paperplane"
+        case let value where value.contains("trash"): "trash"
+        case let value where value.contains("draft"): "doc"
+        default: "folder"
+        }
+    }
+}
+
+struct MailAttachment: Identifiable, Sendable {
+    var id = UUID()
+    let name: String
+    let mimeType: String
+    let data: Data
+}
+
+struct MailMessage: Identifiable, Sendable {
+    let id: String
+    let sender: String
+    let recipient: String
+    let subject: String
+    let date: Date
+    let body: String
+    let attachments: [MailAttachment]
+    var isRead = false
+}
+
+enum MailError: LocalizedError {
+    case message(String)
+    var errorDescription: String? {
+        switch self { case .message(let text): text }
+    }
+}
+
+enum PasswordStore {
+    private static func query(_ id: UUID) -> [String: Any] {
+        [kSecClass as String: kSecClassGenericPassword,
+         kSecAttrService as String: "de.mikemail.account",
+         kSecAttrAccount as String: id.uuidString]
+    }
+
+    static func save(_ password: String, for id: UUID) throws {
+        let attributes = [kSecValueData as String: Data(password.utf8)]
+        let status = SecItemUpdate(query(id) as CFDictionary, attributes as CFDictionary)
+        if status == errSecItemNotFound {
+            var entry = query(id)
+            entry.merge(attributes) { _, new in new }
+            entry[kSecAttrAccessible as String] = kSecAttrAccessibleWhenUnlocked
+            let result = SecItemAdd(entry as CFDictionary, nil)
+            guard result == errSecSuccess else { throw MailError.message("Passwort konnte nicht im Schlüsselbund gespeichert werden (\(result)).") }
+        } else if status != errSecSuccess {
+            throw MailError.message("Schlüsselbundfehler (\(status)).")
+        }
+    }
+
+    static func delete(for id: UUID) throws {
+        let status = SecItemDelete(query(id) as CFDictionary)
+        guard status == errSecSuccess || status == errSecItemNotFound else {
+            throw MailError.message("Passwort konnte nicht entfernt werden (\(status)).")
+        }
+    }
+
+    static func password(for id: UUID) throws -> String {
+        var entry = query(id)
+        entry[kSecReturnData as String] = true
+        entry[kSecMatchLimit as String] = kSecMatchLimitOne
+        var result: CFTypeRef?
+        let status = SecItemCopyMatching(entry as CFDictionary, &result)
+        guard status == errSecSuccess, let data = result as? Data,
+              let value = String(data: data, encoding: .utf8) else {
+            throw MailError.message("Bitte unter „Konten“ das Passwort für dieses Konto speichern.")
+        }
+        return value
+    }
+}

MikeMail/MailSMTP.c

@@ -0,0 +1,81 @@
+#include "MailSMTP.h"
+#include <curl/curl.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static pthread_once_t curl_once = PTHREAD_ONCE_INIT;
+static void initialize_curl(void) { curl_global_init(CURL_GLOBAL_DEFAULT); }
+
+struct MessageReader {
+    const unsigned char *bytes;
+    size_t length;
+    size_t offset;
+};
+
+static size_t read_message(char *destination, size_t size, size_t count, void *context) {
+    struct MessageReader *reader = context;
+    size_t available = reader->length - reader->offset;
+    size_t requested = size * count;
+    size_t copied = available < requested ? available : requested;
+    memcpy(destination, reader->bytes + reader->offset, copied);
+    reader->offset += copied;
+    return copied;
+}
+
+int mail_smtp_send(const char *host, unsigned short port, const char *username,
+                   const char *password, const char *sender, const char *recipients,
+                   const unsigned char *message, size_t length,
+                   char *error, size_t errorCapacity) {
+    pthread_once(&curl_once, initialize_curl);
+    CURL *curl = curl_easy_init();
+    if (!curl) {
+        snprintf(error, errorCapacity, "SMTP konnte nicht initialisiert werden.");
+        return CURLE_FAILED_INIT;
+    }
+    char url[1024];
+    snprintf(url, sizeof(url), "%s://%s:%u", port == 465 ? "smtps" : "smtp", host, port);
+    char detail[CURL_ERROR_SIZE] = {0};
+    struct MessageReader reader = { message, length, 0 };
+    struct curl_slist *addresses = NULL;
+    char *copy = strdup(recipients);
+    if (!copy) { curl_easy_cleanup(curl); return CURLE_OUT_OF_MEMORY; }
+    char *save = NULL;
+    for (char *address = strtok_r(copy, "\n", &save); address; address = strtok_r(NULL, "\n", &save)) {
+        struct curl_slist *next = curl_slist_append(addresses, address);
+        if (!next) {
+            free(copy);
+            curl_slist_free_all(addresses);
+            curl_easy_cleanup(curl);
+            return CURLE_OUT_OF_MEMORY;
+        }
+        addresses = next;
+    }
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+    // Require STARTTLS on submission ports; never authenticate over plaintext.
+    curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);
+    curl_easy_setopt(curl, CURLOPT_USERNAME, username);
+    curl_easy_setopt(curl, CURLOPT_PASSWORD, password);
+    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, sender);
+    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, addresses);
+    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_message);
+    curl_easy_setopt(curl, CURLOPT_READDATA, &reader);
+    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
+    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, (curl_off_t)length);
+    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 25L);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 90L);
+    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1L);
+    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, detail);
+    CURLcode result = curl_easy_perform(curl);
+    if (result != CURLE_OK) {
+        snprintf(error, errorCapacity, "%s%s", detail[0] ? detail : curl_easy_strerror(result),
+                 reader.offset > 0 ? " — Versandstatus möglicherweise unklar; vor erneutem Senden Eingang prüfen." : "");
+    }
+    free(copy);
+    curl_slist_free_all(addresses);
+    curl_easy_cleanup(curl);
+    return (int)result;
+}

MikeMail/MailSMTP.h

@@ -0,0 +1,9 @@
+#ifndef MailSMTP_h
+#define MailSMTP_h
+#include <stddef.h>
+
+int mail_smtp_send(const char *host, unsigned short port, const char *username,
+                   const char *password, const char *sender, const char *recipients,
+                   const unsigned char *message, size_t length,
+                   char *error, size_t errorCapacity);
+#endif

MikeMail/MailStore.swift

@@ -0,0 +1,174 @@
+import Foundation
+import Observation
+
+@MainActor @Observable
+final class MailStore {
+    var accounts: [MailAccount] = []
+    var recipientHistory: [String] = []
+    var folders: [UUID: [MailFolder]] = [:]
+    var messages: [MailMessage] = []
+    var isBusy = false
+    var totalMessages = 0
+    var status = "Lokales Archiv bereit."
+    var error: String?
+    private var archive: MailArchive?
+    private var selectedFolderID: String?
+
+    init(archive: MailArchive? = nil) {
+        do {
+            let storage = try archive ?? MailArchive()
+            self.archive = storage
+            if let configuration = try storage.configuration() {
+                accounts = configuration.accounts
+                folders = configuration.folders
+                recipientHistory = configuration.recipients
+            } else {
+                if let data = UserDefaults.standard.data(forKey: "mailAccounts") {
+                    accounts = try JSONDecoder().decode([MailAccount].self, from: data)
+                } else { accounts = [.testAccount] }
+                recipientHistory = UserDefaults.standard.stringArray(forKey: "recipientHistory") ?? []
+                try persist()
+            }
+        } catch {
+            self.error = "Lokales Archiv konnte nicht geöffnet werden: \(error.localizedDescription)"
+            status = "Archivfehler – vorhandene Daten wurden nicht ersetzt."
+        }
+    }
+
+    private func storage() throws -> MailArchive {
+        guard let archive else { throw MailError.message("Lokales Archiv ist nicht verfügbar.") }
+        return archive
+    }
+
+    private func persist() throws {
+        try storage().saveConfiguration(ArchiveConfiguration(accounts: accounts, folders: folders, recipients: recipientHistory))
+    }
+
+    func save(account: MailAccount, password: String) throws {
+        guard !isBusy else { throw MailError.message("Bitte den laufenden Abruf abwarten.") }
+        guard MIME.validAddress(account.email), !account.username.isEmpty,
+              !account.host.isEmpty, !account.host.contains(where: { $0.isWhitespace || $0 == "/" }),
+              account.imapPort > 0, account.smtpPort > 0 else {
+            throw MailError.message("Bitte E-Mail-Adresse, Benutzername, Server und Ports prüfen.")
+        }
+        let archive = try storage()
+        if let old = accounts.first(where: { $0.id == account.id }),
+           old.host != account.host || old.username != account.username || old.email != account.email {
+            throw MailError.message("Für eine andere Server-, Benutzer- oder Mailadresse bitte ein neues Konto anlegen. So bleiben archivierte Mails eindeutig zugeordnet.")
+        }
+        var updated = accounts
+        if let index = updated.firstIndex(where: { $0.id == account.id }) { updated[index] = account }
+        else { updated.append(account) }
+        if !password.isEmpty { try PasswordStore.save(password, for: account.id) }
+        try archive.saveConfiguration(ArchiveConfiguration(accounts: updated, folders: folders, recipients: recipientHistory))
+        accounts = updated
+        status = "Konto lokal gespeichert."
+    }
+
+    func deleteAccount(id: UUID) throws {
+        guard !isBusy else { throw MailError.message("Bitte den laufenden Abruf abwarten.") }
+        let archive = try storage()
+        let remaining = accounts.filter { $0.id != id }
+        var remainingFolders = folders
+        remainingFolders[id] = nil
+        try archive.saveConfiguration(ArchiveConfiguration(accounts: remaining, folders: remainingFolders, recipients: recipientHistory))
+        accounts = remaining
+        folders = remainingFolders
+        messages = []
+        totalMessages = 0
+        try PasswordStore.delete(for: id)
+        status = "Konto entfernt; archivierte Originalmails und Serverdaten bleiben erhalten."
+    }
+
+    private func allFolders(_ items: [MailFolder]) -> [MailFolder] {
+        items.flatMap { [$0] + allFolders($0.children ?? []) }
+    }
+
+    func refresh(folderID: String?) async {
+        guard !isBusy else { return }
+        isBusy = true
+        defer { isBusy = false }
+        var failures: [String] = []
+        do {
+            let archive = try storage()
+            for account in accounts {
+                do {
+                    let client = try IMAPClient(account: account)
+                    defer { client.close() }
+                    status = "\(account.email): Verbindung wird aufgebaut …"
+                    try await client.login(account: account, password: PasswordStore.password(for: account.id))
+                    let discovered = try await client.folders(accountID: account.id)
+                    // Keep the previous listing if saving the new configuration fails.
+                    var updated = folders
+                    updated[account.id] = discovered
+                    try archive.saveConfiguration(ArchiveConfiguration(accounts: accounts, folders: updated, recipients: recipientHistory))
+                    folders = updated
+                    for folder in allFolders(discovered) where folder.selectable {
+                        do {
+                            status = "\(folder.name): Änderungen prüfen …"
+                            let inventory = try await client.inventory(folder: folder)
+                            let known = try archive.knownUIDs(folderID: folder.id, validity: inventory.validity)
+                            let missing = Set(inventory.flags.keys).subtracting(known).sorted(by: >)
+                            for (index, uid) in missing.enumerated() {
+                                try Task.checkCancellation()
+                                status = "\(folder.name): \(index + 1) von \(missing.count) neuen Mails speichern …"
+                                let raw = try await client.rawMessage(uid: uid)
+                                try archive.store(raw: raw, folderID: folder.id, validity: inventory.validity,
+                                    uid: String(uid), flags: inventory.flags[uid] ?? [], visible: false)
+                            }
+                            try archive.reconcile(folderID: folder.id, inventory: inventory)
+                            if selectedFolderID == folder.id { try display(folderID: folder.id) }
+                        } catch { failures.append("\(account.email) / \(folder.name): \(error.localizedDescription)") }
+                    }
+                } catch { failures.append("\(account.email): \(error.localizedDescription)") }
+            }
+            if let selectedFolderID { try display(folderID: selectedFolderID) }
+        } catch { failures.append(error.localizedDescription) }
+        if failures.isEmpty {
+            status = "Abgleich abgeschlossen. Alle abgerufenen Mails sind offline verfügbar."
+        } else {
+            error = failures.joined(separator: "\n")
+            status = "Abgleich unvollständig. Bereits gespeicherte Mails bleiben offline verfügbar."
+        }
+    }
+
+    private func display(folderID: String) throws {
+        messages = try storage().messages(folderID: folderID)
+        totalMessages = messages.count
+    }
+
+    func load(folderID: String?, more: Bool = false) async {
+        selectedFolderID = folderID
+        guard let folderID else { messages = []; totalMessages = 0; return }
+        do {
+            try display(folderID: folderID)
+            if !isBusy { status = "\(messages.count) lokal gespeicherte Nachrichten · Abrufen gleicht Änderungen ab." }
+        } catch { self.error = error.localizedDescription }
+    }
+
+    func send(accountID: UUID?, recipients: String, subject: String, body: String, attachments: [MailAttachment]) async throws {
+        guard let account = accounts.first(where: { $0.id == accountID }) else {
+            throw MailError.message("Bitte ein Absenderkonto auswählen.")
+        }
+        let archive = try storage()
+        let addresses = recipients.split(separator: ",").map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+        let data = try MIME.compose(from: account.email, to: addresses, subject: subject, body: body, attachments: attachments)
+        let localFolder = MailFolder(accountID: account.id, path: "__local_outgoing__", name: "Lokale Versandkopien")
+        let localID = UUID().uuidString
+        // Persist BEFORE SMTP, so a crash or uncertain delivery cannot lose the composed message.
+        try archive.store(raw: data, folderID: localFolder.id, validity: "local", uid: localID, flags: ["Pending"])
+        try await SMTPClient.send(account: account, password: PasswordStore.password(for: account.id), recipients: addresses, message: data)
+        do {
+            try archive.store(raw: data, folderID: localFolder.id, validity: "local", uid: localID, flags: ["\\Seen", "Sent"])
+            for address in addresses {
+                recipientHistory.removeAll { $0.caseInsensitiveCompare(address) == .orderedSame }
+                recipientHistory.insert(address, at: 0)
+            }
+            try persist()
+            status = "Nachricht versendet und lokal archiviert."
+        } catch {
+            // SMTP already succeeded: do not offer an accidental resend by throwing here.
+            self.error = "Nachricht wurde versendet; Archivstatus konnte nicht aktualisiert werden: \(error.localizedDescription)"
+        }
+    }
+}

MikeMail/MailTransport.swift

@@ -0,0 +1,128 @@
+import Foundation
+import Network
+
+/// One sequential protocol session. TLS uses the system trust store and hostname validation.
+@MainActor
+final class TLSConnection {
+    private let connection: NWConnection
+    private var buffer = Data()
+    private var connectionContinuation: CheckedContinuation<Void, Error>?
+    private var deadline: Task<Void, Never>?
+
+    init(host: String, port: UInt16) throws {
+        guard let endpointPort = NWEndpoint.Port(rawValue: port), !host.isEmpty else {
+            throw MailError.message("Ungültiger Server oder Port.")
+        }
+        connection = NWConnection(host: NWEndpoint.Host(host), port: endpointPort, using: .tls)
+    }
+
+    func open() async throws {
+        try await withCheckedThrowingContinuation { continuation in
+            connectionContinuation = continuation
+            connection.stateUpdateHandler = { [weak self] state in
+                Task { @MainActor in
+                    guard let self else { return }
+                    switch state {
+                    case .ready: self.finishOpen(nil)
+                    case .failed(let error), .waiting(let error): self.finishOpen(error)
+                    case .cancelled: self.finishOpen(MailError.message("Verbindung beendet."))
+                    default: break
+                    }
+                }
+            }
+            connection.start(queue: .global(qos: .userInitiated))
+            deadline = Task { [weak self] in
+                try? await Task.sleep(for: .seconds(25))
+                guard !Task.isCancelled else { return }
+                self?.finishOpen(MailError.message("Zeitüberschreitung beim Verbindungsaufbau."))
+                self?.connection.cancel()
+            }
+        }
+    }
+
+    private func finishOpen(_ error: Error?) {
+        guard let continuation = connectionContinuation else { return }
+        connectionContinuation = nil
+        deadline?.cancel()
+        if let error { continuation.resume(throwing: error) }
+        else { continuation.resume() }
+    }
+
+    func close() { deadline?.cancel(); connection.cancel() }
+
+    func send(_ data: Data) async throws {
+        let timeout = Task { [connection] in
+            try? await Task.sleep(for: .seconds(30))
+            if !Task.isCancelled { connection.cancel() }
+        }
+        defer { timeout.cancel() }
+        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in
+            connection.send(content: data, completion: .contentProcessed { error in
+                if let error { continuation.resume(throwing: error) }
+                else { continuation.resume() }
+            })
+        }
+    }
+
+    func line(_ text: String) async throws { try await send(Data((text + "\r\n").utf8)) }
+
+    private func receive() async throws {
+        let timeout = Task { [connection] in
+            try? await Task.sleep(for: .seconds(30))
+            if !Task.isCancelled { connection.cancel() }
+        }
+        defer { timeout.cancel() }
+        let data: Data = try await withCheckedThrowingContinuation { continuation in
+            connection.receive(minimumIncompleteLength: 1, maximumLength: 65_536) { data, _, complete, error in
+                if let error { continuation.resume(throwing: error) }
+                else if let data, !data.isEmpty { continuation.resume(returning: data) }
+                else { continuation.resume(throwing: MailError.message(complete ? "Der Server hat die Verbindung beendet." : "Keine Serverantwort.")) }
+            }
+        }
+        buffer.append(data)
+    }
+
+    func readLine() async throws -> String {
+        while true {
+            if let range = buffer.range(of: Data("\r\n".utf8)) {
+                let data = buffer[..<range.lowerBound]
+                let value = String(decoding: data, as: UTF8.self)
+                buffer.removeSubrange(..<range.upperBound)
+                return value
+            }
+            guard buffer.count < 1_000_000 else { throw MailError.message("Serverantwort ist zu lang.") }
+            try await receive()
+        }
+    }
+
+    func readBytes(_ count: Int) async throws -> Data {
+        guard count >= 0, count <= 40_000_000 else { throw MailError.message("Nachricht überschreitet das Limit von 40 MB.") }
+        while buffer.count < count { try await receive() }
+        let data = Data(buffer.prefix(count))
+        buffer.removeFirst(count)
+        return data
+    }
+}
+
+enum SMTPClient {
+    static func send(account: MailAccount, password: String, recipients: [String], message: Data) async throws {
+        guard MIME.validAddress(account.email), !recipients.isEmpty, recipients.allSatisfy(MIME.validAddress) else {
+            throw MailError.message("Ungültige E-Mail-Adresse.")
+        }
+        let host = account.host
+        let port = account.smtpPort
+        let username = account.username
+        let sender = account.email
+        let addresses = recipients.joined(separator: "\n")
+        // libcurl runs on a worker, so TLS negotiation and uploads never block the UI.
+        let result = await Task.detached(priority: .userInitiated) {
+            var error = [CChar](repeating: 0, count: 1024)
+            let code = message.withUnsafeBytes { bytes in
+                mail_smtp_send(host, port, username, password, sender, addresses,
+                    bytes.bindMemory(to: UInt8.self).baseAddress, message.count, &error, error.count)
+            }
+            return (code, String(cString: error))
+        }.value
+        guard result.0 == 0 else { throw MailError.message("SMTP: \(result.1) (\(result.0))") }
+    }
+}

MikeMail/MikeMailApp.swift

@@ -1,32 +1,13 @@
-//
-//  MikeMailApp.swift
-//  MikeMail
-//
-//  Created by Dr. med. Michael Kübler on 06.11.26.
-//
-
 import SwiftUI
-import SwiftData
 
 @main
 struct MikeMailApp: App {
-    var sharedModelContainer: ModelContainer = {
-        let schema = Schema([
-            Item.self,
-        ])
-        let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)
-
-        do {
-            return try ModelContainer(for: schema, configurations: [modelConfiguration])
-        } catch {
-            fatalError("Could not create ModelContainer: \(error)")
-        }
-    }()
+    @State private var store = MailStore()
 
     var body: some Scene {
         WindowGroup {
-            ContentView()
+            ContentView(store: store)
         }
-        .modelContainer(sharedModelContainer)
+        .defaultSize(width: 1200, height: 800)
     }
 }

MikeMail/RecipientField.swift

@@ -0,0 +1,129 @@
+import SwiftUI
+import AppKit
+import Contacts
+import ContactsUI
+
+enum RecipientCompletion {
+    static func matches(in history: [String], input: String) -> [String] {
+        let parts = input.components(separatedBy: ",")
+        let query = (parts.last ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !query.isEmpty else { return [] }
+        let selected = Set(parts.dropLast().map { $0.trimmingCharacters(in: .whitespacesAndNewlines).lowercased() })
+        return history.filter {
+            !selected.contains($0.lowercased()) && $0.localizedCaseInsensitiveContains(query)
+                && $0.caseInsensitiveCompare(query) != .orderedSame
+        }
+    }
+
+    static func inserting(_ address: String, into input: String) -> String {
+        var parts = input.components(separatedBy: ",").dropLast().map {
+            $0.trimmingCharacters(in: .whitespacesAndNewlines)
+        }.filter { !$0.isEmpty }
+        if !parts.contains(where: { $0.caseInsensitiveCompare(address) == .orderedSame }) { parts.append(address) }
+        return parts.joined(separator: ", ") + ", "
+    }
+}
+
+/// The system picker includes iCloud contacts synchronized with macOS Contacts.
+/// Only the email address explicitly selected by the user is passed to MikeMail.
+struct ContactPickerButton: NSViewRepresentable {
+    var onSelect: (String) -> Void
+
+    func makeCoordinator() -> Coordinator { Coordinator(onSelect: onSelect) }
+
+    func makeNSView(context: Context) -> NSButton {
+        let button = NSButton(image: NSImage(systemSymbolName: "person.crop.square", accessibilityDescription: "Adressbuch") ?? NSImage(),
+                              target: context.coordinator, action: #selector(Coordinator.show(_:)))
+        button.bezelStyle = .rounded
+        button.toolTip = "Empfänger aus Kontakten auswählen (einschließlich iCloud)"
+        button.setAccessibilityLabel("Adressbuch")
+        return button
+    }
+
+    func updateNSView(_ nsView: NSButton, context: Context) { context.coordinator.onSelect = onSelect }
+
+    static func dismantleNSView(_ nsView: NSButton, coordinator: Coordinator) { coordinator.picker.close() }
+
+    final class Coordinator: NSObject, CNContactPickerDelegate {
+        let picker = CNContactPicker()
+        var onSelect: (String) -> Void
+
+        init(onSelect: @escaping (String) -> Void) {
+            self.onSelect = onSelect
+            super.init()
+            picker.delegate = self
+            picker.displayedKeys = [CNContactEmailAddressesKey]
+        }
+
+        @objc func show(_ sender: NSButton) {
+            picker.showRelative(to: sender.bounds, of: sender, preferredEdge: .maxY)
+        }
+
+        func contactPicker(_ picker: CNContactPicker, didSelect contactProperty: CNContactProperty) {
+            guard contactProperty.key == CNContactEmailAddressesKey,
+                  let email = contactProperty.value as? String else { return }
+            onSelect(email)
+            picker.close()
+        }
+    }
+}
+
+struct RecipientField: View {
+    @Binding var recipient: String
+    let history: [String]
+    @FocusState private var focused: Bool
+    @State private var highlighted = 0
+
+    var body: some View {
+        let suggestions = RecipientCompletion.matches(in: history, input: recipient)
+        VStack(alignment: .leading, spacing: 4) {
+            HStack {
+                ContactPickerButton { address in
+                    recipient = RecipientCompletion.inserting(address, into: recipient)
+                    focused = true
+                }.frame(width: 30, height: 26)
+                TextField("An (mehrere mit Komma trennen)", text: $recipient)
+                    .accessibilityIdentifier("recipientField")
+                    .focused($focused)
+                    .onKeyPress(.downArrow) {
+                        guard !suggestions.isEmpty else { return .ignored }
+                        highlighted = min(highlighted + 1, suggestions.count - 1)
+                        return .handled
+                    }
+                    .onKeyPress(.upArrow) {
+                        guard !suggestions.isEmpty else { return .ignored }
+                        highlighted = max(0, highlighted - 1)
+                        return .handled
+                    }
+                    .onKeyPress(.return) {
+                        guard suggestions.indices.contains(highlighted) else { return .ignored }
+                        recipient = RecipientCompletion.inserting(suggestions[highlighted], into: recipient)
+                        return .handled
+                    }
+            }
+            if focused && !suggestions.isEmpty {
+                ScrollViewReader { proxy in
+                    ScrollView {
+                        LazyVStack(alignment: .leading, spacing: 0) {
+                            ForEach(Array(suggestions.enumerated()), id: \.element) { index, address in
+                                Button {
+                                    recipient = RecipientCompletion.inserting(address, into: recipient)
+                                    focused = true
+                                } label: {
+                                    Text(address).frame(maxWidth: .infinity, alignment: .leading).padding(6)
+                                        .background(index == highlighted ? Color.accentColor.opacity(0.15) : .clear)
+                                }
+                                .buttonStyle(.plain)
+                                .id(index)
+                            }
+                        }
+                    }
+                    .frame(height: min(CGFloat(suggestions.count) * 30, 120))
+                    .onChange(of: highlighted) { _, index in proxy.scrollTo(index) }
+                }
+                .padding(.leading, 38)
+            }
+        }
+        .onChange(of: recipient) { _, _ in highlighted = 0 }
+    }
+}

MikeMailTests/MailArchiveTests.swift

@@ -0,0 +1,65 @@
+import Foundation
+import Testing
+@testable import MikeMail
+
+@MainActor
+struct MailArchiveTests {
+    @Test func diskPersistenceIncrementalReconciliationAndRestore() throws {
+        let base = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: base) }
+        let root = base.appending(path: "Archive")
+        let account = MailAccount(name: "Fixture", email: "fixture@example.com", username: "fixture", host: "example.com")
+        let folder = MailFolder(accountID: account.id, path: "INBOX", name: "Posteingang")
+        let bytes = Data((0...255).map(UInt8.init))
+        let raw = try MIME.compose(from: account.email, to: ["recipient@example.com"], subject: "Offline Büro",
+            body: "Dauerhaft verfügbar", attachments: [MailAttachment(name: "Prüfung.bin", mimeType: "application/octet-stream", data: bytes)])
+        var archive: MailArchive? = try MailArchive(root: root)
+        try archive?.saveConfiguration(ArchiveConfiguration(accounts: [account], folders: [account.id: [folder]], recipients: ["recipient@example.com"]))
+        try archive?.store(raw: raw, folderID: folder.id, validity: "10", uid: "1", flags: [])
+        try archive?.store(raw: raw, folderID: folder.id, validity: "10", uid: "1", flags: ["\\Seen"])
+        #expect(try archive?.messages(folderID: folder.id).count == 1)
+        #expect(try archive?.knownUIDs(folderID: folder.id, validity: "10") == [1])
+        #expect(try archive?.knownUIDs(folderID: folder.id, validity: "11") == [])
+        archive = nil
+
+        let reopened = try MailArchive(root: root)
+        #expect(try reopened.configuration()?.accounts == [account])
+        #expect(try reopened.messages(folderID: folder.id).first?.attachments.first?.data == bytes)
+        #expect(try reopened.messages(folderID: folder.id).first?.isRead == true)
+        try reopened.reconcile(folderID: folder.id, inventory: MailboxInventory(validity: "10", flags: [1: []]))
+        #expect(try reopened.messages(folderID: folder.id).first?.isRead == false)
+        // Partial download of a new UID generation is durable but not mixed into the visible old generation.
+        try reopened.store(raw: raw, folderID: folder.id, validity: "11", uid: "2", flags: [], visible: false)
+        #expect(try reopened.messages(folderID: folder.id).count == 1)
+        #expect(try reopened.knownUIDs(folderID: folder.id, validity: "11") == [2])
+        let backup = base.appending(path: "Backup")
+        try reopened.exportSnapshot(to: backup)
+        let restored = try MailArchive.restoreSnapshot(from: backup, to: base.appending(path: "Restored"))
+        #expect(try restored.messages(folderID: folder.id).first?.body == "Dauerhaft verfügbar")
+        #expect(try restored.messages(folderID: folder.id).first?.attachments.first?.data == bytes)
+        #expect(try restored.configuration()?.recipients == ["recipient@example.com"])
+
+        // A server UIDVALIDITY reset must not attach old data to the reused UID.
+        try reopened.reconcile(folderID: folder.id, inventory: MailboxInventory(validity: "11", flags: [1: []]))
+        #expect(try reopened.messages(folderID: folder.id).isEmpty)
+        let retained = base.appending(path: "RetainedBackup")
+        try reopened.exportSnapshot(to: retained)
+        let manifest = try JSONDecoder().decode(MailArchive.Snapshot.self, from: Data(contentsOf: retained.appending(path: "manifest.json")))
+        #expect(manifest.messages.count == 2)
+        #expect(manifest.messages.allSatisfy { !$0.present })
+        let object = retained.appending(path: "Objects/\(MailArchive.digest(raw)).eml")
+        try Data("corrupt".utf8).write(to: object)
+        #expect(throws: (any Error).self) {
+            try MailArchive.restoreSnapshot(from: retained, to: base.appending(path: "Rejected"))
+        }
+        #expect(!FileManager.default.fileExists(atPath: base.appending(path: "Rejected").path))
+    }
+
+    @Test func imapInventoryParsing() throws {
+        #expect(try IMAPClient.uidValidity(from: ["* OK [UIDVALIDITY 123] UIDs valid"]) == "123")
+        #expect(throws: (any Error).self) { try IMAPClient.uidValidity(from: ["* OK hello"]) }
+        let flags = try IMAPClient.parseFlags(["* 1 FETCH (UID 7 FLAGS (\\Seen \\Flagged))", "* 2 FETCH (FLAGS () UID 9)"])
+        #expect(flags[7] == ["\\Seen", "\\Flagged"])
+        #expect(flags[9] == [])
+    }
+}

MikeMailTests/MikeMailTests.swift

@@ -1,19 +1,91 @@
-//
-//  MikeMailTests.swift
-//  MikeMailTests
-//
-//  Created by Dr. med. Michael Kübler on 06.11.26.
-//
-
+import Foundation
 import Testing
 @testable import MikeMail
 
+@MainActor
 struct MikeMailTests {
-
-    @Test func example() async throws {
-        // Write your test here and use APIs like `#expect(...)` to check expected conditions.
-        // Swift Testing Documentation
-        // https://developer.apple.com/documentation/testing
+    @Test func recipientSuggestionsAndInsertion() {
+        let history = ["anna@example.com", "bert@example.com", "anna@work.de"]
+        #expect(RecipientCompletion.matches(in: history, input: "ANN") == ["anna@example.com", "anna@work.de"])
+        #expect(RecipientCompletion.matches(in: history, input: "anna@example.com, ann") == ["anna@work.de"])
+        #expect(RecipientCompletion.matches(in: history, input: "") == [])
+        #expect(RecipientCompletion.inserting("bert@example.com", into: "anna@example.com, be") == "anna@example.com, bert@example.com, ")
+        #expect(RecipientCompletion.inserting("anna@example.com", into: "anna@example.com, an") == "anna@example.com, ")
     }
 
+    @Test func imapEscapingAndMailboxNames() throws {
+        #expect(try IMAPClient.quote("Ordner \"Büro\"") == "\"Ordner \\\"Büro\\\"\"")
+        #expect(throws: (any Error).self) { try IMAPClient.quote("INBOX\r\nDELETE INBOX") }
+        #expect(IMAPClient.tokens("\"/\" \"Ordner mit Leerzeichen\"") == ["/", "Ordner mit Leerzeichen"])
+        #expect(IMAPClient.decodeMailbox("B&APw-ro") == "Büro")
+        #expect(IMAPClient.decodeMailbox("A &- B") == "A & B")
+    }
+
+    @Test func binaryAttachmentRoundTrip() throws {
+        let bytes = Data((0...255).map(UInt8.init))
+        let attachment = MailAttachment(name: "Büroprüfung.bin", mimeType: "application/octet-stream", data: bytes)
+        let raw = try MIME.compose(from: "sender@example.com", to: ["recipient@example.com"],
+            subject: "Grüße aus dem Büro", body: "Zeile 1\n.\nÄÖÜ ß", attachments: [attachment])
+        let decoded = MIME.parse(raw, id: "1")
+        #expect(decoded.subject == "Grüße aus dem Büro")
+        #expect(decoded.body == "Zeile 1\n.\nÄÖÜ ß")
+        #expect(decoded.attachments.count == 1)
+        #expect(decoded.attachments.first?.name == "Büroprüfung.bin")
+        #expect(decoded.attachments.first?.data == bytes)
+    }
+
+    @Test func incomingNestedMIME() {
+        let raw = """
+        From: =?UTF-8?Q?J=C3=B6rg?= <joerg@example.com>
+        Subject: =?UTF-8?B?R3LDvMOfZQ==?=
+        Date: Fri, 06 Nov 2026 10:30:00 +0100
+        Content-Type: multipart/mixed; boundary="outer"
+
+        --outer
+        Content-Type: multipart/alternative; boundary="inner"
+
+        --inner
+        Content-Type: text/plain; charset=utf-8
+        Content-Transfer-Encoding: quoted-printable
+
+        Gr=C3=BC=C3=9Fe aus dem B=C3=BCro.
+        --inner
+        Content-Type: text/html; charset=utf-8
+
+        <p>Alternative</p>
+        --inner--
+        --outer
+        Content-Type: application/pdf
+        Content-Disposition: attachment; filename="rechnung.pdf"
+        Content-Transfer-Encoding: base64
+
+        JVBERi0xLjc=
+        --outer--
+        """
+        let message = MIME.parse(Data(raw.replacingOccurrences(of: "\n", with: "\r\n").utf8), id: "2")
+        #expect(message.sender == "Jörg <joerg@example.com>")
+        #expect(message.subject == "Grüße")
+        #expect(message.body == "Grüße aus dem Büro.")
+        #expect(message.attachments.first?.name == "rechnung.pdf")
+        #expect(message.attachments.first?.data == Data("%PDF-1.7".utf8))
+        #expect(message.date != .distantPast)
+    }
+
+    @Test func foldedHeaderAndQuotedPrintable() {
+        #expect(MIME.decodeHeader("=?UTF-8?Q?Gr=C3=BC=C3=9Fe?= =?UTF-8?Q?_Welt?=") == "Grüße Welt")
+        #expect(MIME.headers("Subject: Erste\r\n zweite\r\nFrom: a@example.com")["subject"] == "Erste zweite")
+        #expect(MIME.quotedPrintable(Data("a=\r\nb=3Dc".utf8)) == Data("ab=c".utf8))
+    }
+
+    @Test func preventsHeaderInjection() {
+        #expect(throws: (any Error).self) {
+            try MIME.compose(from: "a@example.com", to: ["b@example.com\r\nBcc: x@example.com"],
+                subject: "Hallo", body: "", attachments: [])
+        }
+        #expect(throws: (any Error).self) {
+            try MIME.compose(from: "a@example.com", to: ["b@example.com"],
+                subject: "Hallo\r\nBcc: x@example.com", body: "", attachments: [])
+        }
+        #expect(!MIME.validAddress("not an address"))
+    }
 }

MikeMailUITests/MikeMailUITests.swift

@@ -1,43 +1,30 @@
-//
-//  MikeMailUITests.swift
-//  MikeMailUITests
-//
-//  Created by Dr. med. Michael Kübler on 06.11.26.
-//
-
 import XCTest
+import XCUIAutomation
 
 final class MikeMailUITests: XCTestCase {
-
-    override func setUpWithError() throws {
-        // Put setup code here. This method is called before the invocation of each test method in the class.
-
-        // In UI tests it is usually best to stop immediately when a failure occurs.
+    @MainActor
+    func testMailWindowAndCompose() throws {
         continueAfterFailure = false
-
-        // In UI tests it’s important to set the initial state - such as interface orientation - required for your tests before they run. The setUp method is a good place to do this.
-    }
-
-    override func tearDownWithError() throws {
-        // Put teardown code here. This method is called after the invocation of each test method in the class.
-    }
-
-    @MainActor
-    func testExample() throws {
-        // UI tests must launch the application that they test.
         let app = XCUIApplication()
+        app.launchArguments = ["-ApplePersistenceIgnoreState", "YES"]
         app.launch()
-
-        // Use XCTAssert and related functions to verify your tests produce the correct results.
-        // XCUIAutomation Documentation
-        // https://developer.apple.com/documentation/xcuiautomation
-    }
-
-    @MainActor
-    func testLaunchPerformance() throws {
-        // This measures how long it takes to launch your application.
-        measure(metrics: [XCTApplicationLaunchMetric()]) {
-            XCUIApplication().launch()
-        }
+        app.activate()
+        XCTAssertTrue(app.buttons["Neue Nachricht"].waitForExistence(timeout: 5), app.debugDescription)
+        XCTAssertTrue(app.staticTexts["Nachricht auswählen"].waitForExistence(timeout: 5), app.debugDescription)
+        app.buttons["Neue Nachricht"].click()
+        XCTAssertTrue(app.buttons["Anhang hinzufügen"].waitForExistence(timeout: 5))
+        XCTAssertFalse(app.buttons["Senden"].isEnabled)
+        XCTAssertTrue(app.buttons["Adressbuch"].exists)
+        XCTAssertTrue(app.textFields["recipientField"].exists)
+        app.buttons["Abbrechen"].click()
+        app.buttons["Konten"].click()
+        XCTAssertTrue(app.secureTextFields.firstMatch.waitForExistence(timeout: 5))
+        XCTAssertTrue(app.buttons["Speichern"].exists)
+        XCTAssertTrue(app.buttons["Neues Konto hinzufügen"].exists)
+        XCTAssertTrue(app.buttons["Konto löschen"].exists)
+        app.buttons["Neues Konto hinzufügen"].click()
+        XCTAssertTrue(app.textFields["accountEmail"].waitForExistence(timeout: 5))
+        app.buttons["Schließen"].click()
+        XCTAssertTrue(app.buttons["Abrufen"].exists)
     }
 }