diff --git a/MikeMail/AccountOrderDrop.swift b/MikeMail/AccountOrderDrop.swift
new file mode 100644
index 0000000..8e12736
--- /dev/null
+++ b/MikeMail/AccountOrderDrop.swift
@@ -0,0 +1,279 @@
+import SwiftUI
+
+/// Flattened tree entries give each account and folder its own native table row and drop target.
+struct SidebarEntry: Identifiable, Equatable {
+    let id: String
+    var account: MailAccount?
+    var folder: MailFolder?
+    var depth = 0
+    var title: String
+    var icon: String
+
+    static func visible(accounts: [MailAccount], folders: [UUID: [MailFolder]], inbox: Bool, trash: Bool,
+                        expanded: (String) -> Bool) -> [SidebarEntry] {
+        var entries: [SidebarEntry] = []
+        if inbox { entries.append(SidebarEntry(id: "unified:inbox", title: "Gemeinsamer Posteingang", icon: "tray.2")) }
+        if trash { entries.append(SidebarEntry(id: "unified:trash", title: "Gemeinsamer Papierkorb", icon: "trash")) }
+        func appendFolders(_ children: [MailFolder], depth: Int) {
+            for folder in children {
+                entries.append(SidebarEntry(id: folder.id, folder: folder, depth: depth,
+                    title: folder.name, icon: folder.isTrash ? "trash" : folder.icon))
+                if expanded("folderExpanded." + folder.id), let children = folder.children {
+                    appendFolders(children, depth: depth + 1)
+                }
+            }
+        }
+        for account in accounts {
+            entries.append(SidebarEntry(id: "account:" + account.id.uuidString, account: account,
+                title: account.name.isEmpty ? account.email : account.name, icon: "person.crop.circle"))
+            if expanded("accountExpanded." + account.id.uuidString) {
+                appendFolders(folders[account.id] ?? [], depth: 1)
+            }
+        }
+        return entries
+    }
+
+    static func destination(_ offset: Int, rows: [SidebarEntry], accounts: [MailAccount]) -> Int {
+        guard offset < rows.count else { return accounts.count }
+        // A drop within an account's folders goes before the next account, keeping the whole tree together.
+        let next = rows.dropFirst(max(0, offset)).compactMap(\.account).first
+        return next.flatMap { account in accounts.firstIndex { $0.id == account.id } } ?? accounts.count
+    }
+}
+
+
+struct MailSidebarList: NSViewRepresentable {
+    let store: MailStore
+    @Binding var selection: String?
+    let showInbox: Bool
+    let showTrash: Bool
+    let create: (UUID, MailFolder?) -> Void
+    let delete: (MailFolder) -> Void
+    let empty: (String) -> Void
+
+    func makeCoordinator() -> Coordinator { Coordinator(self) }
+
+    func makeNSView(context: Context) -> NSScrollView {
+        let scroll = NSScrollView()
+        scroll.hasVerticalScroller = true
+        scroll.drawsBackground = false
+        let table = NSTableView()
+        let column = NSTableColumn(identifier: NSUserInterfaceItemIdentifier("sidebar"))
+        table.addTableColumn(column)
+        table.headerView = nil
+        table.backgroundColor = .clear
+        table.selectionHighlightStyle = .sourceList
+        table.columnAutoresizingStyle = .uniformColumnAutoresizingStyle
+        table.intercellSpacing = NSSize(width: 0, height: 2)
+        table.delegate = context.coordinator
+        table.dataSource = context.coordinator
+        table.setDraggingSourceOperationMask(.move, forLocal: true)
+        table.registerForDraggedTypes([Coordinator.accountType, .string])
+        table.setAccessibilityIdentifier("accountSidebar")
+        let menu = NSMenu()
+        menu.delegate = context.coordinator
+        table.menu = menu
+        scroll.documentView = table
+        context.coordinator.table = table
+        return scroll
+    }
+
+    func updateNSView(_ scroll: NSScrollView, context: Context) {
+        context.coordinator.parent = self
+        context.coordinator.reload()
+    }
+
+    final class Coordinator: NSObject, NSTableViewDataSource, NSTableViewDelegate, NSMenuDelegate {
+        static let accountType = NSPasteboard.PasteboardType("de.mikemail.account-order")
+        var parent: MailSidebarList
+        weak var table: NSTableView?
+        var rows: [SidebarEntry] = []
+        var reloading = false
+        var displayedCounts: [String: Int] = [:]
+
+        init(_ parent: MailSidebarList) { self.parent = parent }
+
+        func expanded(_ key: String) -> Bool {
+            UserDefaults.standard.object(forKey: key) as? Bool ?? true
+        }
+
+        func reload(force: Bool = false) {
+            reloading = true
+            let updated = SidebarEntry.visible(accounts: parent.store.accounts, folders: parent.store.folders,
+                inbox: parent.showInbox, trash: parent.showTrash, expanded: expanded)
+            let counts = parent.store.unreadCounts
+            if force || updated != rows || counts != displayedCounts {
+                rows = updated
+                displayedCounts = counts
+                table?.reloadData()
+            }
+            if let index = rows.firstIndex(where: { $0.id == parent.selection }) {
+                if table?.selectedRow != index { table?.selectRowIndexes(IndexSet(integer: index), byExtendingSelection: false) }
+            } else if table?.selectedRow != -1 { table?.deselectAll(nil) }
+            reloading = false
+        }
+
+        func numberOfRows(in tableView: NSTableView) -> Int { rows.count }
+        func tableView(_ tableView: NSTableView, heightOfRow row: Int) -> CGFloat {
+            rows[row].account == nil ? 30 : 46
+        }
+        func tableView(_ tableView: NSTableView, shouldSelectRow row: Int) -> Bool {
+            rows[row].folder?.selectable != false
+        }
+        func tableViewSelectionDidChange(_ notification: Notification) {
+            guard !reloading, let table, rows.indices.contains(table.selectedRow) else { return }
+            parent.selection = rows[table.selectedRow].id
+        }
+
+        func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? {
+            let entry = rows[row]
+            let cell = NSTableCellView()
+            let stack = NSStackView()
+            stack.orientation = .horizontal
+            stack.distribution = .fill
+            stack.alignment = .centerY
+            stack.spacing = 8
+            stack.translatesAutoresizingMaskIntoConstraints = false
+            cell.addSubview(stack)
+            NSLayoutConstraint.activate([
+                stack.leadingAnchor.constraint(equalTo: cell.leadingAnchor, constant: 8 + CGFloat(entry.depth) * 12),
+                stack.trailingAnchor.constraint(equalTo: cell.trailingAnchor, constant: -8),
+                stack.centerYAnchor.constraint(equalTo: cell.centerYAnchor)
+            ])
+            let key = entry.account.map { "accountExpanded." + $0.id.uuidString }
+                ?? (entry.folder?.children?.isEmpty == false ? "folderExpanded." + entry.id : nil)
+            if let key {
+                let button = NSButton(image: NSImage(systemSymbolName: expanded(key) ? "chevron.down" : "chevron.right",
+                    accessibilityDescription: expanded(key) ? "Zuklappen" : "Aufklappen") ?? NSImage(),
+                    target: self, action: #selector(toggle(_:)))
+                button.isBordered = false
+                button.identifier = NSUserInterfaceItemIdentifier(key)
+                button.setAccessibilityIdentifier(key)
+                button.widthAnchor.constraint(equalToConstant: 16).isActive = true
+                stack.addArrangedSubview(button)
+            } else {
+                let spacer = NSView()
+                spacer.widthAnchor.constraint(equalToConstant: 16).isActive = true
+                stack.addArrangedSubview(spacer)
+            }
+            let icon = NSImageView(image: NSImage(systemSymbolName: entry.icon, accessibilityDescription: nil) ?? NSImage())
+            icon.contentTintColor = .controlAccentColor
+            icon.widthAnchor.constraint(equalToConstant: 18).isActive = true
+            stack.addArrangedSubview(icon)
+            let texts = NSStackView()
+            texts.orientation = .vertical
+            texts.alignment = .leading
+            texts.spacing = 2
+            let title = NSTextField(labelWithString: entry.title)
+            title.lineBreakMode = .byTruncatingTail
+            title.font = .systemFont(ofSize: 13)
+            texts.addArrangedSubview(title)
+            if let account = entry.account {
+                let email = NSTextField(labelWithString: account.email)
+                email.font = .systemFont(ofSize: 11)
+                email.textColor = .secondaryLabelColor
+                email.lineBreakMode = .byTruncatingTail
+                texts.addArrangedSubview(email)
+                cell.setAccessibilityIdentifier("accountRow-" + account.email)
+            }
+            texts.setContentHuggingPriority(.defaultLow, for: .horizontal)
+            stack.addArrangedSubview(texts)
+            if entry.account != nil {
+                let handle = NSImageView(image: NSImage(systemSymbolName: "line.3.horizontal", accessibilityDescription: "Konto verschieben") ?? NSImage())
+                handle.widthAnchor.constraint(equalToConstant: 18).isActive = true
+                handle.toolTip = "Kontenzeile an die gewünschte Position ziehen"
+                stack.addArrangedSubview(handle)
+            } else {
+                let count = parent.store.unreadCount(folderID: entry.id)
+                if count > 0 { stack.addArrangedSubview(NSTextField(labelWithString: String(count))) }
+            }
+            return cell
+        }
+
+        @objc func toggle(_ sender: NSButton) {
+            guard let key = sender.identifier?.rawValue else { return }
+            UserDefaults.standard.set(!expanded(key), forKey: key)
+            reload(force: true)
+        }
+
+        func tableView(_ tableView: NSTableView, pasteboardWriterForRow row: Int) -> (any NSPasteboardWriting)? {
+            guard let account = rows[row].account else { return nil }
+            let item = NSPasteboardItem()
+            item.setString(account.id.uuidString, forType: Self.accountType)
+            return item
+        }
+
+        func tableView(_ tableView: NSTableView, validateDrop info: any NSDraggingInfo,
+                       proposedRow row: Int, proposedDropOperation operation: NSTableView.DropOperation) -> NSDragOperation {
+            if info.draggingPasteboard.string(forType: Self.accountType) != nil {
+                tableView.setDropRow(row, dropOperation: .above)
+                return .move
+            }
+            if rows.indices.contains(row), rows[row].folder?.selectable == true,
+               let value = info.draggingPasteboard.string(forType: .string), !MailDrag.decode(value).isEmpty {
+                tableView.setDropRow(row, dropOperation: .on)
+                return .move
+            }
+            return []
+        }
+
+        func tableView(_ tableView: NSTableView, acceptDrop info: any NSDraggingInfo,
+                       row: Int, dropOperation: NSTableView.DropOperation) -> Bool {
+            if let value = info.draggingPasteboard.string(forType: Self.accountType),
+               let id = UUID(uuidString: value),
+               let source = parent.store.accounts.firstIndex(where: { $0.id == id }) {
+                parent.store.moveAccounts(from: IndexSet(integer: source),
+                    to: SidebarEntry.destination(row, rows: rows, accounts: parent.store.accounts))
+                reload()
+                return true
+            }
+            guard rows.indices.contains(row), let folder = rows[row].folder,
+                  folder.selectable, let value = info.draggingPasteboard.string(forType: .string) else { return false }
+            let ids = MailDrag.decode(value)
+            guard !ids.isEmpty else { return false }
+            Task { await parent.store.moveMessages(ids: ids, to: folder) }
+            return true
+        }
+
+        func menuNeedsUpdate(_ menu: NSMenu) {
+            menu.removeAllItems()
+            guard let table, rows.indices.contains(table.clickedRow) else { return }
+            let row = rows[table.clickedRow]
+            func add(_ title: String, _ action: String, enabled: Bool = true) {
+                let item = NSMenuItem(title: title, action: #selector(menuAction(_:)), keyEquivalent: "")
+                item.target = self
+                item.representedObject = [row.id, action]
+                item.isEnabled = enabled
+                menu.addItem(item)
+            }
+            menu.autoenablesItems = false
+            if let account = row.account, let index = parent.store.accounts.firstIndex(where: { $0.id == account.id }) {
+                add("Neuen Ordner erstellen…", "create")
+                add("Konto nach oben", "up", enabled: index > 0)
+                add("Konto nach unten", "down", enabled: index + 1 < parent.store.accounts.count)
+            } else if let folder = row.folder {
+                add("Unterordner erstellen…", "create")
+                add("Ordner löschen…", "delete", enabled: !folder.isInbox)
+                if folder.isTrash { add("Papierkorb leeren…", "empty") }
+            } else if row.id == "unified:trash" { add("Papierkorb leeren…", "empty") }
+        }
+
+        @objc func menuAction(_ item: NSMenuItem) {
+            guard let values = item.representedObject as? [String], values.count == 2,
+                  let row = rows.first(where: { $0.id == values[0] }) else { return }
+            switch values[1] {
+            case "create":
+                if let account = row.account { parent.create(account.id, nil) }
+                else if let folder = row.folder { parent.create(folder.accountID, folder) }
+            case "delete": if let folder = row.folder { parent.delete(folder) }
+            case "empty": parent.empty(row.id)
+            case "up", "down":
+                if let account = row.account, let index = parent.store.accounts.firstIndex(where: { $0.id == account.id }) {
+                    parent.store.moveAccounts(from: IndexSet(integer: index), to: values[1] == "up" ? index - 1 : index + 2)
+                    reload()
+                }
+            default: break
+            }
+        }
+    }
+}
diff --git a/MikeMail/ContentView.swift b/MikeMail/ContentView.swift
index b29ec61..6b8c82e 100644
--- a/MikeMail/ContentView.swift
+++ b/MikeMail/ContentView.swift
@@ -17,12 +17,12 @@ struct ContentView: View {
     @State private var selectedFolder: String?
     @State private var selectedMessages: Set<String> = []
     @State private var showingAccounts = false
-    @State private var composing = false
-    @State private var draft: ComposeDraft?
     @Environment(\.openWindow) private var openWindow
     @AppStorage("idleEnabled") private var idleEnabled = true
     @AppStorage("pollMinutes") private var pollMinutes = 5
     @AppStorage("mailDeleteConfirmation") private var deleteConfirmation: MailDeleteConfirmation = .always
+    @AppStorage("markReadImmediately") private var markReadImmediately = false
+    @AppStorage("markReadDelaySeconds") private var markReadDelaySeconds = 1
     @State private var pendingDeletion: [String] = []
     @State private var confirmingDelete = false
     @State private var restored = false
@@ -71,7 +71,6 @@ struct ContentView: View {
                 }
                 .frame(height: 26)
                 .padding(8)
-                .disabled(store.isBusy)
                 VSplitView {
                     MessageTable(messages: store.messages.filter(searchFilter.matches), selection: $selectedMessages, busy: store.isBusy, action: perform)
                         .onDeleteCommand { deleteSelection() }
@@ -116,17 +115,15 @@ struct ContentView: View {
                 }
                 .accessibilityIdentifier("Abrufen")
                 .disabled(store.isBusy)
-                Button("Neue Nachricht", systemImage: "square.and.pencil") { composing = true }
+                Button("Neue Nachricht", systemImage: "square.and.pencil") { openComposer(ComposeDraft(accountID: composeAccountID)) }
                     .keyboardShortcut("n", modifiers: .command).disabled(store.accounts.isEmpty)
                 Button("Löschen", systemImage: "trash") { deleteSelection() }
-                    .disabled(selectedMessages.isEmpty || store.isBusy)
+                    .disabled(selectedMessages.isEmpty)
                 Button("Konten", systemImage: "person.crop.circle") { showingAccounts = true }
                 SettingsLink { Label("Einstellungen", systemImage: "gearshape") }
             }
         }
         .sheet(isPresented: $showingAccounts) { AccountsView(store: store) }
-        .sheet(isPresented: $composing) { ComposeView(store: store, defaultAccountID: composeAccountID) }
-        .sheet(item: $draft) { ComposeView(store: store, draft: $0) }
         .sheet(item: Binding(get: { store.authenticationAccount }, set: { value in
             if value == nil { store.dismissPasswordRequest() }
         })) { account in
@@ -136,11 +133,13 @@ struct ContentView: View {
             store.configureIdle(enabled: idleEnabled)
         }
         .task(id: pollMinutes) { await store.poll(intervalMinutes: pollMinutes) }
-        .task(id: selectedMessages) {
+        .task(id: AutoReadRequest(ids: selectedMessages, immediately: markReadImmediately, seconds: markReadDelaySeconds)) {
             guard selectedMessages.count == 1, let id = selectedMessages.first,
                   let message = store.message(id: id), !message.isRead else { return }
-            try? await Task.sleep(for: .milliseconds(700))
-            if !Task.isCancelled { await store.setRead(ids: [id], read: true) }
+            do {
+                try await AutoReadRequest(ids: [id], immediately: markReadImmediately, seconds: markReadDelaySeconds).wait()
+                await store.setRead(ids: [id], read: true)
+            } catch { /* Selection changed before the read delay elapsed. */ }
         }
         .alert(pendingDeletion.count == 1 ? "Nachricht löschen?" : "\(pendingDeletion.count) Nachrichten löschen?", isPresented: $confirmingDelete) {
             Button("Abbrechen", role: .cancel) {}
@@ -179,6 +178,10 @@ struct ContentView: View {
         .frame(minWidth: 850, minHeight: 550)
     }
 
+    private func openComposer(_ draft: ComposeDraft) {
+        openWindow(id: "compose", value: store.prepareCompose(draft))
+    }
+
     private func perform(_ command: MessageCommand, _ ids: Set<String>) {
         guard !ids.isEmpty else { return }
         switch command {
@@ -186,7 +189,7 @@ struct ContentView: View {
             if ids.count == 1, let id = ids.first { openWindow(id: "message", value: id) }
         case .reply, .forward:
             if ids.count == 1, let id = ids.first, let message = store.message(id: id) {
-                draft = .from(message, accountID: store.accountID(for: id), forwarding: command == .forward)
+                openComposer(.from(message, accountID: store.accountID(for: id), forwarding: command == .forward))
             }
         case .delete:
             requestDeletion(Array(ids))
@@ -196,12 +199,12 @@ struct ContentView: View {
     }
 
     private func deleteSelection() {
-        guard !store.isBusy, !selectedMessages.isEmpty else { return }
+        guard !selectedMessages.isEmpty else { return }
         requestDeletion(Array(selectedMessages))
     }
 
     private func requestDeletion(_ ids: [String]) {
-        guard !store.isBusy, !ids.isEmpty else { return }
+        guard !ids.isEmpty else { return }
         if deleteConfirmation.isRequired(count: ids.count) {
             pendingDeletion = ids
             confirmingDelete = true
@@ -258,22 +261,10 @@ struct AccountSidebar: View {
     @State private var confirmingTrash = false
 
     var body: some View {
-        List(selection: $selection) {
-            if showInbox {
-                HStack { Label("Gemeinsamer Posteingang", systemImage: "tray.2"); Spacer(); UnreadBadge(count: store.unreadCount(folderID: "unified:inbox")) }.tag("unified:inbox")
-            }
-            if showTrash {
-                HStack { Label("Gemeinsamer Papierkorb", systemImage: "trash"); Spacer(); UnreadBadge(count: store.unreadCount(folderID: "unified:trash")) }.tag("unified:trash")
-                    .contextMenu { Button("Papierkorb leeren…") { confirmTrash("unified:trash") }.disabled(store.isBusy) }
-            }
-            ForEach(store.accounts) { account in
-                AccountTree(store: store, account: account, selection: $selection,
-                    create: { parent in beginCreate(account.id, parent: parent) },
-                    delete: { folder in deleting = folder; confirmingFolder = true },
-                    empty: { confirmTrash($0.id) })
-            }
-        }
-        .listStyle(.sidebar)
+        MailSidebarList(store: store, selection: $selection, showInbox: showInbox, showTrash: showTrash,
+            create: { beginCreate($0, parent: $1) },
+            delete: { deleting = $0; confirmingFolder = true },
+            empty: confirmTrash)
         .onChange(of: showInbox) { _, visible in if !visible && selection == "unified:inbox" { selection = nil } }
         .onChange(of: showTrash) { _, visible in if !visible && selection == "unified:trash" { selection = nil } }
         .alert("Neuen Ordner erstellen", isPresented: $creating) {
@@ -308,113 +299,6 @@ struct AccountSidebar: View {
     private func confirmTrash(_ id: String) { trashID = id; confirmingTrash = true }
 }
 
-struct AccountTree: View {
-    let store: MailStore
-    let account: MailAccount
-    @Binding var selection: String?
-    let create: (MailFolder?) -> Void
-    let delete: (MailFolder) -> Void
-    let empty: (MailFolder) -> Void
-    @AppStorage private var expanded: Bool
-
-    init(store: MailStore, account: MailAccount, selection: Binding<String?>,
-         create: @escaping (MailFolder?) -> Void, delete: @escaping (MailFolder) -> Void,
-         empty: @escaping (MailFolder) -> Void) {
-        self.store = store; self.account = account; _selection = selection
-        self.create = create; self.delete = delete; self.empty = empty
-        _expanded = AppStorage(wrappedValue: true, "accountExpanded.\(account.id)")
-    }
-
-    var body: some View {
-        DisclosureGroup(isExpanded: $expanded) {
-            ForEach(store.folders[account.id] ?? []) { folder in
-                FolderTree(store: store, folder: folder, create: create, delete: delete, empty: empty)
-            }
-            if store.folders[account.id] == nil {
-                Text("Zum Laden „Abrufen“ wählen").font(.caption).foregroundStyle(.secondary).selectionDisabled()
-            }
-        } label: {
-            Label {
-                VStack(alignment: .leading) {
-                    Text(account.name.isEmpty ? account.email : account.name)
-                    Text(account.email).font(.caption).foregroundStyle(.secondary)
-                }
-            } icon: {
-                Image(systemName: "person.crop.circle")
-            }
-            .draggable("mikemail-account:" + account.id.uuidString)
-            .dropDestination(for: String.self) { values, _ in
-                guard !store.isBusy, let value = values.first, value.hasPrefix("mikemail-account:"),
-                      let id = UUID(uuidString: String(value.dropFirst("mikemail-account:".count))) else { return false }
-                store.reorderAccount(id, before: account.id)
-                return true
-            }
-            .contextMenu {
-                Button("Neuen Ordner erstellen…") { create(nil) }
-                if let index = store.accounts.firstIndex(where: { $0.id == account.id }) {
-                    Button("Konto nach oben") {
-                        store.reorderAccount(account.id, before: store.accounts[index - 1].id)
-                    }.disabled(index == 0)
-                    Button("Konto nach unten") {
-                        store.reorderAccount(store.accounts[index + 1].id, before: account.id)
-                    }.disabled(index + 1 == store.accounts.count)
-                }
-            }
-            .disabled(store.isBusy)
-        }
-        .tag("account:" + account.id.uuidString)
-    }
-}
-
-struct FolderTree: View {
-    let store: MailStore
-    let folder: MailFolder
-    let create: (MailFolder?) -> Void
-    let delete: (MailFolder) -> Void
-    let empty: (MailFolder) -> Void
-    @AppStorage private var expanded: Bool
-
-    init(store: MailStore, folder: MailFolder, create: @escaping (MailFolder?) -> Void,
-         delete: @escaping (MailFolder) -> Void, empty: @escaping (MailFolder) -> Void) {
-        self.store = store; self.folder = folder
-        self.create = create; self.delete = delete; self.empty = empty
-        _expanded = AppStorage(wrappedValue: true, "folderExpanded.\(folder.id)")
-    }
-    var body: some View {
-        Group {
-            if let children = folder.children, !children.isEmpty {
-                DisclosureGroup(isExpanded: $expanded) {
-                    ForEach(children) { child in
-                        FolderTree(store: store, folder: child, create: create, delete: delete, empty: empty)
-                    }
-                } label: { label }
-            } else { label }
-        }
-        .tag(folder.id).selectionDisabled(!folder.selectable)
-    }
-
-    private var label: some View {
-        HStack {
-            Label(folder.name, systemImage: folder.isTrash ? "trash" : folder.icon)
-            Spacer()
-            UnreadBadge(count: store.unreadCount(folderID: folder.id))
-        }
-            .contentShape(Rectangle())
-            .dropDestination(for: String.self) { values, _ in
-                guard !store.isBusy, folder.selectable else { return false }
-                let ids = values.flatMap(MailDrag.decode)
-                guard !ids.isEmpty else { return false }
-                Task { await store.moveMessages(ids: ids, to: folder) }
-                return true
-            }
-            .contextMenu {
-                Button("Unterordner erstellen…") { create(folder) }
-                Button("Ordner löschen…", role: .destructive) { delete(folder) }.disabled(folder.isInbox)
-                if folder.isTrash { Button("Papierkorb leeren…", role: .destructive) { empty(folder) } }
-            }.disabled(store.isBusy)
-    }
-}
-
 struct MessageTable: View {
     let messages: [MailMessage]
     @Binding var selection: Set<String>
@@ -431,12 +315,12 @@ struct MessageTable: View {
                     Image(systemName: "paperclip").accessibilityLabel(message.attachments.count == 1 ? "Ein Anhang" : "\(message.attachments.count) Anhänge")
                 }
             }.width(55)
-            TableColumn("Absender", value: \.sender) { message in
-                Text(message.sender).fontWeight(message.isRead ? .regular : .bold)
+            TableColumn("Absender", value: \.displaySender) { message in
+                Text(message.displaySender).fontWeight(message.isRead ? .regular : .bold)
             }.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()).fontWeight(message.isRead ? .regular : .bold) }
+                else { Text(MailDisplay.date(message.date)).monospacedDigit().fontWeight(message.isRead ? .regular : .bold) }
             }.width(min: 120, ideal: 150)
             TableColumn("Betreff", value: \.subject) { message in
                 Text(message.subject).fontWeight(message.isRead ? .regular : .bold)
@@ -449,9 +333,9 @@ struct MessageTable: View {
         .contextMenu(forSelectionType: String.self) { ids in
             if ids.count == 1 {
                 Button("In neuem Fenster öffnen") { action(.open, ids) }
-                MessageActionButtons { action($0, ids) }.disabled(busy)
+                MessageActionButtons { action($0, ids) }
             } else if !ids.isEmpty {
-                Button("Nachrichten löschen…") { action(.delete, ids) }.disabled(busy)
+                Button("Nachrichten löschen…") { action(.delete, ids) }
             }
             if !ids.isEmpty {
                 Divider()
@@ -462,7 +346,7 @@ struct MessageTable: View {
         .onAppear {
             let order: SortOrder = savedAscending ? .forward : .reverse
             switch savedColumn {
-            case "sender": sortOrder = [KeyPathComparator(\MailMessage.sender, order: order)]
+            case "sender": sortOrder = [KeyPathComparator(\MailMessage.displaySender, order: order)]
             case "subject": sortOrder = [KeyPathComparator(\MailMessage.subject, order: order)]
             case "attachments": sortOrder = [KeyPathComparator(\MailMessage.attachmentCount, order: order)]
             default: sortOrder = [KeyPathComparator(\MailMessage.date, order: order)]
@@ -472,7 +356,7 @@ struct MessageTable: View {
             guard let first = value.first else { return }
             savedAscending = first.order == .forward
             switch first.keyPath {
-            case \MailMessage.sender: savedColumn = "sender"
+            case \MailMessage.displaySender: savedColumn = "sender"
             case \MailMessage.subject: savedColumn = "subject"
             case \MailMessage.attachmentCount: savedColumn = "attachments"
             default: savedColumn = "date"
@@ -502,6 +386,8 @@ enum MailDrag {
 
 struct MessageReader: View {
     let message: MailMessage?
+    @AppStorage("bodyFontName") private var bodyFontName = "Helvetica"
+    @AppStorage("bodyFontSize") private var bodyFontSize = 14.0
     var body: some View {
         ScrollView {
             if let message {
@@ -516,7 +402,13 @@ struct MessageReader: View {
                         }
                     }.textSelection(.enabled)
                     Divider()
-                    Text(message.body).textSelection(.enabled).frame(maxWidth: .infinity, alignment: .leading)
+                    if let html = message.htmlBody {
+                        HTMLMessageBody(html: html, attachments: message.attachments)
+                            .id(message.id)
+                    } else {
+                        Text(message.body).font(.custom(bodyFontName, size: bodyFontSize))
+                            .textSelection(.enabled).frame(maxWidth: .infinity, alignment: .leading)
+                    }
                     if !message.attachments.isEmpty {
                         AttachmentList(attachments: message.attachments)
                             .padding(16)
@@ -544,13 +436,15 @@ struct ComposeView: View {
     @State private var cc = ""
     @State private var bcc = ""
     @State private var subject = ""
-    @State private var text = ""
+    @State private var editor = MailEditorModel()
+    @State private var htmlEnabled = true
+    @AppStorage("bodyFontName") private var bodyFontName = "Helvetica"
+    @AppStorage("bodyFontSize") private var bodyFontSize = 14.0
     @State private var attachments: [MailAttachment] = []
     @State private var importing = false
     @State private var sending = false
     @State private var initialized = false
     @State private var dropTargeted = false
-    @FocusState private var bodyFocused: Bool
     @State private var error: String?
 
     var body: some View {
@@ -565,8 +459,12 @@ struct ComposeView: View {
                 TextField("BCC", text: $bcc).accessibilityIdentifier("composeBCC")
                 TextField("Betreff", text: $subject)
             }
-            TextEditor(text: $text).font(.body).frame(minHeight: 180).border(.quaternary)
-                .focused($bodyFocused)
+            Toggle("HTML-Nachricht", isOn: $htmlEnabled)
+            if htmlEnabled { MailFormattingBar(editor: editor) }
+            MailBodyEditor(model: editor, initialText: draft?.body ?? "",
+                fontName: bodyFontName, fontSize: bodyFontSize, focusOnOpen: draft?.isReply == true,
+                richText: htmlEnabled)
+                .frame(minHeight: 180, maxHeight: .infinity).border(.quaternary)
             VStack(alignment: .leading, spacing: 8) {
                 Label(attachments.count == 1 ? "Anhang – Dateien hier ablegen" : "Anhänge – Dateien hier ablegen", systemImage: "paperclip").font(.headline)
                 ScrollView {
@@ -602,7 +500,8 @@ struct ComposeView: View {
                     Task {
                         do {
                             try await store.send(accountID: accountID, recipients: recipient, cc: cc, bcc: bcc,
-                                subject: subject, body: text, attachments: attachments)
+                                subject: subject, body: editor.plainText, attachments: attachments,
+                                htmlBody: htmlEnabled ? try editor.html() : nil)
                             dismiss()
                         } catch { self.error = error.localizedDescription }
                         sending = false
@@ -612,7 +511,8 @@ struct ComposeView: View {
                 .disabled(MailStore.addresses(recipient + "," + cc + "," + bcc).isEmpty || accountID == nil)
             }
         }
-        .padding(24).frame(width: 700, height: 740)
+        .padding(24)
+        .frame(minWidth: 640, idealWidth: 760, maxWidth: .infinity, minHeight: 600, idealHeight: 780, maxHeight: .infinity)
         .disabled(sending)
         .interactiveDismissDisabled(sending)
         .onAppear {
@@ -621,9 +521,7 @@ struct ComposeView: View {
             accountID = draft?.accountID ?? defaultAccountID ?? store.accounts.first?.id
             recipient = draft?.recipient ?? ""
             subject = draft?.subject ?? ""
-            text = draft?.body ?? ""
             attachments = draft?.attachments ?? []
-            if draft?.isReply == true { bodyFocused = true }
         }
         .fileImporter(isPresented: $importing, allowedContentTypes: [.data], allowsMultipleSelection: true) { result in
             do { addAttachments(try result.get()) }
diff --git a/MikeMail/IMAPClient.swift b/MikeMail/IMAPClient.swift
index 540f917..c813ee2 100644
--- a/MikeMail/IMAPClient.swift
+++ b/MikeMail/IMAPClient.swift
@@ -232,8 +232,39 @@ final class IMAPClient {
         _ = try await command("UID STORE \(uid) \(read ? "+" : "-")FLAGS.SILENT (\\Seen)")
     }
 
-    func move(uid: UInt64, to path: String) async throws {
-        _ = try await command("UID MOVE \(uid) \(Self.quote(path))")
+    struct AssignedUID: Equatable {
+        let validity: String
+        let uid: String
+    }
+
+    /// Single-message COPYUID/APPENDUID responses identify the local destination record.
+    static func assignedUID(_ lines: [String], sourceUID: UInt64? = nil) -> AssignedUID? {
+        let code = sourceUID == nil ? "APPENDUID" : "COPYUID"
+        for line in lines {
+            guard let start = line.range(of: "[" + code + " ", options: .caseInsensitive),
+                  let end = line[start.upperBound...].firstIndex(of: "]") else { continue }
+            let parts = line[start.upperBound..<end].split(separator: " ").map(String.init)
+            guard parts.count == (sourceUID == nil ? 2 : 3),
+                  let validity = UInt64(parts[0]), validity > 0,
+                  let uid = UInt64(parts[parts.count - 1]), uid > 0 else { continue }
+            if let sourceUID, UInt64(parts[1]) != sourceUID { continue }
+            return AssignedUID(validity: String(validity), uid: String(uid))
+        }
+        return nil
+    }
+
+    /// Select and inspect only the requested UID, without enumerating the mailbox.
+    func messageInventory(folder: MailFolder, uid: UInt64) async throws -> MailboxInventory {
+        let selected = try await command("SELECT \(Self.quote(folder.path))")
+        let validity = try Self.uidValidity(from: selected.lines)
+        let fetched = try await command("UID FETCH \(uid) (UID FLAGS)")
+        return MailboxInventory(validity: validity, flags: try Self.parseFlags(fetched.lines))
+    }
+
+    @discardableResult
+    func move(uid: UInt64, to path: String) async throws -> AssignedUID? {
+        let result = try await command("UID MOVE \(uid) \(Self.quote(path))")
+        return Self.assignedUID(result.lines, sourceUID: uid)
     }
 
     /// UID EXPUNGE must never be replaced by EXPUNGE: other clients may have marked unrelated mail.
@@ -249,7 +280,8 @@ final class IMAPClient {
         }
     }
 
-    func append(_ message: Data, path: String, flags: [String]) async throws {
+    @discardableResult
+    func append(_ message: Data, path: String, flags: [String]) async throws -> AssignedUID? {
         let allowed = ["\\Seen", "\\Answered", "\\Flagged", "\\Draft"]
         let safeFlags = flags.filter { allowed.contains($0) }.joined(separator: " ")
         sequence += 1
@@ -258,7 +290,8 @@ final class IMAPClient {
         let ready = try await connection.readLine()
         guard ready.hasPrefix("+") else { throw MailError.message("Nachricht konnte nicht im Ziel gespeichert werden: \(ready)") }
         try await connection.send(message + Data("\r\n".utf8))
-        _ = try await response(tag: tag)
+        let result = try await response(tag: tag)
+        return Self.assignedUID(result.lines)
     }
 
     static func encodeMailbox(_ value: String) -> String {
diff --git a/MikeMail/MIME.swift b/MikeMail/MIME.swift
index cf48262..e992d4d 100644
--- a/MikeMail/MIME.swift
+++ b/MikeMail/MIME.swift
@@ -93,8 +93,9 @@ enum MIME {
         }
         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, cc: decodeHeader(fields["cc"] ?? ""), replyTo: decodeHeader(fields["reply-to"] ?? ""))
+            date: date ?? .distantPast, body: bodies.isEmpty ? plainText(htmlBodies.joined(separator: "\n")) : bodies.joined(separator: "\n"),
+            attachments: attachments, cc: decodeHeader(fields["cc"] ?? ""), replyTo: decodeHeader(fields["reply-to"] ?? ""),
+            htmlBody: htmlBodies.isEmpty ? nil : htmlBodies.joined(separator: "\n"))
     }
 
     private static func parsePart(_ data: Data, depth: Int, bodies: inout [String], htmlBodies: inout [String], attachments: inout [MailAttachment]) {
@@ -127,26 +128,30 @@ enum MIME {
         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))
+            attachments.append(MailAttachment(name: decodeHeader(name ?? "Anhang"), mimeType: type.components(separatedBy: ";")[0], data: decoded,
+                contentID: fields["content-id"]?.trimmingCharacters(in: CharacterSet(charactersIn: "<> "))))
         } 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)
+                htmlBodies.append(value)
             } else { bodies.append(value) }
         }
     }
 
+    static func plainText(_ html: String) -> String {
+        html.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: "&quot;", with: "\"")
+            .replacingOccurrences(of: "&amp;", with: "&")
+    }
+
     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], cc: [String] = [], bcc: [String] = [], subject: String, body: String, attachments: [MailAttachment]) throws -> Data {
+    static func compose(from: String, to: [String], cc: [String] = [], bcc: [String] = [], subject: String, body: String, attachments: [MailAttachment], htmlBody: String? = nil) throws -> Data {
         guard validAddress(from), !(to + cc + bcc).isEmpty, (to + cc + bcc).allSatisfy(validAddress),
               !subject.unicodeScalars.contains(where: { CharacterSet.newlines.contains($0) }) else {
             throw MailError.message("Bitte gültige E-Mail-Adressen und einen einzeiligen Betreff eingeben.")
@@ -163,7 +168,15 @@ enum MIME {
         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"
+        if let htmlBody {
+            let alternative = "Alternative-" + UUID().uuidString
+            result += "--\(boundary)\r\nContent-Type: multipart/alternative; boundary=\"\(alternative)\"\r\n\r\n"
+            result += "--\(alternative)\r\nContent-Type: text/plain; charset=utf-8\r\nContent-Transfer-Encoding: base64\r\n\r\n\(base64(Data(body.utf8)))\r\n"
+            result += "--\(alternative)\r\nContent-Type: text/html; charset=utf-8\r\nContent-Transfer-Encoding: base64\r\n\r\n\(base64(Data(htmlBody.utf8)))\r\n"
+            result += "--\(alternative)--\r\n"
+        } else {
+            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"
diff --git a/MikeMail/MailArchive.swift b/MikeMail/MailArchive.swift
index 4fe6eea..fe2cb33 100644
--- a/MikeMail/MailArchive.swift
+++ b/MikeMail/MailArchive.swift
@@ -172,6 +172,35 @@ final class MailArchive {
         } catch { context.rollback(); throw error }
     }
 
+    /// Apply only a confirmed server change; keep original EML objects available for backups.
+    func applyMessageChange(id: String, destination: String? = nil,
+                            assigned: IMAPClient.AssignedUID? = nil, flags: [String]? = nil,
+                            removed: Bool = true) throws {
+        let key = id
+        guard let row = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchivedMail>(
+            predicate: #Predicate { $0.key == key })).first else {
+            throw MailError.message("Lokale Nachricht nicht gefunden.")
+        }
+        do {
+            if let destination, let assigned {
+                let targetKey = destination + ":" + assigned.validity + ":" + assigned.uid
+                if let target = try context.fetch(FetchDescriptor<MailArchiveSchema.ArchivedMail>(
+                    predicate: #Predicate { $0.key == targetKey })).first {
+                    target.objectHash = row.objectHash
+                    target.flags = flags ?? row.flags
+                    target.present = true
+                } else {
+                    context.insert(MailArchiveSchema.ArchivedMail(key: targetKey, folderID: destination,
+                        validity: assigned.validity, uid: assigned.uid, objectHash: row.objectHash,
+                        flags: flags ?? row.flags))
+                }
+            }
+            if removed { row.present = false }
+            else if let flags { 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)
diff --git a/MikeMail/MailBodyEditor.swift b/MikeMail/MailBodyEditor.swift
new file mode 100644
index 0000000..d390465
--- /dev/null
+++ b/MikeMail/MailBodyEditor.swift
@@ -0,0 +1,168 @@
+import SwiftUI
+import AppKit
+import Observation
+
+@MainActor @Observable
+final class MailEditorModel {
+    @ObservationIgnored weak var textView: NSTextView?
+    var fontName = "Helvetica"
+    var fontSize = 14.0
+    var color = Color.black
+    var bold = false
+    var italic = false
+    var underline = false
+    var strikethrough = false
+
+    var plainText: String { textView?.string ?? "" }
+
+    func html() throws -> String {
+        guard let text = textView?.attributedString() else { return "" }
+        let data = try text.data(from: NSRange(location: 0, length: text.length),
+            documentAttributes: [.documentType: NSAttributedString.DocumentType.html,
+                                 .characterEncoding: String.Encoding.utf8.rawValue])
+        return String(decoding: data, as: UTF8.self)
+    }
+
+    func refreshSelection() {
+        guard let view = textView else { return }
+        let range = view.selectedRange()
+        let attributes = range.length > 0 && range.location < view.attributedString().length
+            ? view.attributedString().attributes(at: range.location, effectiveRange: nil)
+            : view.typingAttributes
+        let font = attributes[.font] as? NSFont ?? NSFont.systemFont(ofSize: 14)
+        fontName = font.familyName ?? "Helvetica"
+        fontSize = font.pointSize
+        let traits = NSFontManager.shared.traits(of: font)
+        bold = traits.contains(.boldFontMask)
+        italic = traits.contains(.italicFontMask)
+        underline = (attributes[.underlineStyle] as? Int ?? 0) != 0
+        strikethrough = (attributes[.strikethroughStyle] as? Int ?? 0) != 0
+        color = Color(nsColor: attributes[.foregroundColor] as? NSColor ?? .textColor)
+    }
+
+    func apply(_ transform: ([NSAttributedString.Key: Any]) -> [NSAttributedString.Key: Any]) {
+        guard let view = textView else { return }
+        let range = view.selectedRange()
+        if range.length > 0, let storage = view.textStorage,
+           view.shouldChangeText(in: range, replacementString: nil) {
+            let before = view.attributedString().attributedSubstring(from: range)
+            let changed = NSMutableAttributedString(attributedString: before)
+            before.enumerateAttributes(in: NSRange(location: 0, length: before.length)) { attributes, subrange, _ in
+                changed.setAttributes(transform(attributes), range: subrange)
+            }
+            storage.replaceCharacters(in: range, with: changed)
+            view.didChangeText()
+            view.setSelectedRange(range)
+        }
+        view.typingAttributes = transform(view.typingAttributes)
+        view.window?.makeFirstResponder(view)
+        refreshSelection()
+    }
+
+    func setFont(name: String? = nil, size: Double? = nil) {
+        apply { attributes in
+            var result = attributes
+            let old = attributes[.font] as? NSFont ?? NSFont.systemFont(ofSize: 14)
+            var font = name.map { NSFontManager.shared.convert(old, toFamily: $0) } ?? old
+            if let size { font = NSFontManager.shared.convert(font, toSize: size) }
+            result[.font] = font
+            return result
+        }
+    }
+
+    func toggleTrait(_ trait: NSFontTraitMask, enabled: Bool) {
+        apply { attributes in
+            var result = attributes
+            let font = attributes[.font] as? NSFont ?? NSFont.systemFont(ofSize: 14)
+            result[.font] = enabled ? NSFontManager.shared.convert(font, toHaveTrait: trait)
+                : NSFontManager.shared.convert(font, toNotHaveTrait: trait)
+            return result
+        }
+    }
+
+    func setAttribute(_ key: NSAttributedString.Key, value: Any) {
+        apply { attributes in
+            var result = attributes
+            result[key] = value
+            return result
+        }
+    }
+}
+
+struct MailFormattingBar: View {
+    @Bindable var editor: MailEditorModel
+    private let fonts = NSFontManager.shared.availableFontFamilies.sorted()
+
+    var body: some View {
+        HStack(spacing: 8) {
+            Picker("Schriftart", selection: Binding(get: { editor.fontName }, set: { editor.setFont(name: $0) })) {
+                ForEach(fonts, id: \.self) { Text($0).tag($0) }
+            }.labelsHidden().frame(maxWidth: 180).help("Schriftart")
+            Picker("Schriftgröße", selection: Binding(get: { editor.fontSize }, set: { editor.setFont(size: $0) })) {
+                ForEach(Array(Set([8, 9, 10, 11, 12, 14, 16, 18, 20, 24, 28, 32, 36, 48, 72, editor.fontSize])).sorted(), id: \.self) {
+                    Text("\($0.formatted())").tag($0)
+                }
+            }.labelsHidden().frame(width: 65).help("Schriftgröße")
+            ColorPicker("Textfarbe", selection: Binding(get: { editor.color }, set: {
+                editor.setAttribute(.foregroundColor, value: NSColor($0))
+            }), supportsOpacity: false).labelsHidden().help("Textfarbe")
+            Button { editor.toggleTrait(.boldFontMask, enabled: !editor.bold) } label: {
+                Image(systemName: "bold").foregroundStyle(editor.bold ? Color.accentColor : .primary)
+            }.help("Fett")
+            Button { editor.toggleTrait(.italicFontMask, enabled: !editor.italic) } label: {
+                Image(systemName: "italic").foregroundStyle(editor.italic ? Color.accentColor : .primary)
+            }.help("Kursiv")
+            Button { editor.setAttribute(.underlineStyle, value: editor.underline ? 0 : NSUnderlineStyle.single.rawValue) } label: {
+                Image(systemName: "underline").foregroundStyle(editor.underline ? Color.accentColor : .primary)
+            }.help("Unterstrichen")
+            Button { editor.setAttribute(.strikethroughStyle, value: editor.strikethrough ? 0 : NSUnderlineStyle.single.rawValue) } label: {
+                Image(systemName: "strikethrough").foregroundStyle(editor.strikethrough ? Color.accentColor : .primary)
+            }.help("Durchgestrichen")
+            Spacer(minLength: 0)
+        }
+        .padding(8).background(.quaternary, in: RoundedRectangle(cornerRadius: 6))
+    }
+}
+
+struct MailBodyEditor: NSViewRepresentable {
+    let model: MailEditorModel
+    let initialText: String
+    let fontName: String
+    let fontSize: Double
+    let focusOnOpen: Bool
+    let richText: Bool
+
+    func makeCoordinator() -> Coordinator { Coordinator(model: model) }
+
+    func makeNSView(context: Context) -> NSScrollView {
+        let scroll = NSTextView.scrollableTextView()
+        guard let view = scroll.documentView as? NSTextView else { return scroll }
+        view.isRichText = richText
+        view.importsGraphics = false
+        view.allowsUndo = true
+        view.isAutomaticQuoteSubstitutionEnabled = false
+        view.textContainerInset = NSSize(width: 8, height: 8)
+        view.font = NSFont(name: fontName, size: fontSize) ?? .systemFont(ofSize: fontSize)
+        view.string = initialText
+        view.setSelectedRange(NSRange(location: 0, length: 0))
+        view.setAccessibilityIdentifier("composeBody")
+        view.delegate = context.coordinator
+        model.textView = view
+        DispatchQueue.main.async {
+            model.refreshSelection()
+            if focusOnOpen { view.window?.makeFirstResponder(view) }
+        }
+        return scroll
+    }
+
+    func updateNSView(_ scroll: NSScrollView, context: Context) {
+        guard let view = scroll.documentView as? NSTextView else { return }
+        view.isRichText = richText
+    }
+
+    final class Coordinator: NSObject, NSTextViewDelegate {
+        let model: MailEditorModel
+        init(model: MailEditorModel) { self.model = model }
+        func textViewDidChangeSelection(_ notification: Notification) { model.refreshSelection() }
+    }
+}
diff --git a/MikeMail/MailModels.swift b/MikeMail/MailModels.swift
index 5cd8537..5dafdec 100644
--- a/MikeMail/MailModels.swift
+++ b/MikeMail/MailModels.swift
@@ -45,6 +45,7 @@ struct MailAttachment: Identifiable, Sendable {
     let name: String
     let mimeType: String
     let data: Data
+    var contentID: String? = nil
 }
 
 struct MailMessage: Identifiable, Sendable {
@@ -58,6 +59,8 @@ struct MailMessage: Identifiable, Sendable {
     var isRead = false
     var cc = ""
     var replyTo = ""
+    var htmlBody: String? = nil
+    var displaySender: String { MailDisplay.sender(sender) }
     var attachmentCount: Int { attachments.count }
 }
 
diff --git a/MikeMail/MailPresentation.swift b/MikeMail/MailPresentation.swift
new file mode 100644
index 0000000..d6144f6
--- /dev/null
+++ b/MikeMail/MailPresentation.swift
@@ -0,0 +1,113 @@
+import SwiftUI
+import AppKit
+import WebKit
+
+enum MailDisplay {
+    static func sender(_ source: String) -> String {
+        guard let bracket = source.firstIndex(of: "<") else { return source }
+        let name = source[..<bracket].trimmingCharacters(in: .whitespaces)
+        guard name.hasPrefix("\""), name.hasSuffix("\""), name.count >= 2 else { return source }
+        let unquoted = name.dropFirst().dropLast()
+            .replacingOccurrences(of: "\\\"", with: "\"")
+            .replacingOccurrences(of: "\\\\", with: "\\")
+        return unquoted + " " + source[bracket...]
+    }
+
+    static func date(_ value: Date, timeZone: TimeZone = .current) -> String {
+        let formatter = DateFormatter()
+        formatter.locale = Locale(identifier: "en_US_POSIX")
+        formatter.timeZone = timeZone
+        formatter.dateFormat = "dd.MM.yyyy HH:mm"
+        return formatter.string(from: value)
+    }
+}
+
+enum MailHTML {
+    static func document(_ html: String, attachments: [MailAttachment], blocked: Bool, font: String, size: Double) -> String {
+        var body = html
+        for attachment in attachments {
+            guard let cid = attachment.contentID, attachment.mimeType.lowercased().hasPrefix("image/"),
+                  !attachment.mimeType.lowercased().contains("svg") else { continue }
+            let dataURL = "data:\(attachment.mimeType);base64,\(attachment.data.base64EncodedString())"
+            body = body.replacingOccurrences(of: "cid:" + cid, with: dataURL)
+        }
+        // The first CSP cannot be weakened by headers or markup in the message.
+        // Scripts, forms, frames, objects and automatic navigation remain disabled even after allowing images.
+        let remote = blocked ? "" : " https: http:"
+        let policy = "default-src 'none'; script-src 'none'; style-src 'unsafe-inline'\(remote); img-src data:\(remote); font-src data:\(remote); media-src 'none'; frame-src 'none'; object-src 'none'; connect-src 'none'; base-uri 'none'; form-action 'none'"
+        let family = font.filter { $0.isLetter || $0.isNumber || $0 == " " || $0 == "-" }
+        return """
+        <!doctype html><html><head><meta charset="utf-8">
+        <meta http-equiv="Content-Security-Policy" content="\(policy)">
+        <meta name="referrer" content="no-referrer">
+        <style>body { font-family: '\(family)', sans-serif; font-size: \(min(48, max(8, size)))px; overflow-wrap: anywhere; } img { max-width: 100%; height: auto; }</style>
+        </head><body>\(body)</body></html>
+        """
+    }
+}
+
+struct HTMLMessageBody: View {
+    let html: String
+    let attachments: [MailAttachment]
+    @AppStorage("blockRemoteContent") private var blockRemoteContent = true
+    @AppStorage("bodyFontName") private var fontName = "Helvetica"
+    @AppStorage("bodyFontSize") private var fontSize = 14.0
+    @State private var allowRemote = false
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            HStack {
+                Label(blockRemoteContent && !allowRemote ? "Externe Inhalte blockiert" : "Externe Inhalte erlaubt",
+                    systemImage: "hand.raised")
+                Spacer()
+                if blockRemoteContent && !allowRemote {
+                    Button("Inhalte laden") { allowRemote = true }
+                }
+            }.font(.caption)
+            HTMLMailView(document: MailHTML.document(html, attachments: attachments,
+                blocked: blockRemoteContent && !allowRemote, font: fontName, size: fontSize))
+                .frame(minHeight: 420)
+        }
+    }
+}
+
+struct HTMLMailView: NSViewRepresentable {
+    let document: String
+
+    func makeCoordinator() -> Coordinator { Coordinator() }
+
+    func makeNSView(context: Context) -> WKWebView {
+        let configuration = WKWebViewConfiguration()
+        configuration.websiteDataStore = .nonPersistent()
+        configuration.defaultWebpagePreferences.allowsContentJavaScript = false
+        let view = WKWebView(frame: .zero, configuration: configuration)
+        view.navigationDelegate = context.coordinator
+        view.setValue(false, forKey: "drawsBackground")
+        return view
+    }
+
+    func updateNSView(_ view: WKWebView, context: Context) {
+        guard context.coordinator.document != document else { return }
+        context.coordinator.document = document
+        view.loadHTMLString(document, baseURL: nil)
+    }
+
+    final class Coordinator: NSObject, WKNavigationDelegate {
+        var document = ""
+
+        func webView(_ webView: WKWebView, decidePolicyFor action: WKNavigationAction,
+                     decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
+            if action.navigationType == .linkActivated, let url = action.request.url,
+               ["https", "http", "mailto"].contains(url.scheme?.lowercased() ?? "") {
+                NSWorkspace.shared.open(url)
+                decisionHandler(.cancel)
+            } else if action.targetFrame?.isMainFrame == true,
+                      action.request.url?.absoluteString == "about:blank",
+                      action.navigationType == .other {
+                decisionHandler(.allow)
+            } else {
+                decisionHandler(.cancel)
+            }
+        }
+    }
+}
diff --git a/MikeMail/MailSettings.swift b/MikeMail/MailSettings.swift
index d840969..8236e91 100644
--- a/MikeMail/MailSettings.swift
+++ b/MikeMail/MailSettings.swift
@@ -13,7 +13,24 @@ enum MailDeleteConfirmation: String {
     }
 }
 
+struct AutoReadRequest: Equatable {
+    let ids: Set<String>
+    let immediately: Bool
+    let seconds: Int
+
+    func wait() async throws {
+        if !immediately { try await Task.sleep(for: .seconds(max(1, seconds))) }
+        try Task.checkCancellation()
+    }
+}
+
 struct MailSettings: View {
+    @AppStorage("markReadImmediately") private var markReadImmediately = false
+    @AppStorage("markReadDelaySeconds") private var markReadDelaySeconds = 1
+    @AppStorage("bodyFontName") private var bodyFontName = "Helvetica"
+    @AppStorage("bodyFontSize") private var bodyFontSize = 14.0
+    @AppStorage("blockRemoteContent") private var blockRemoteContent = true
+    private let fontNames = NSFontManager.shared.availableFontFamilies.sorted()
     @AppStorage("mailDeleteConfirmation") private var deleteConfirmation: MailDeleteConfirmation = .always
     @AppStorage("idleEnabled") private var idleEnabled = true
     @AppStorage("pollMinutes") private var pollMinutes = 5
@@ -24,6 +41,15 @@ struct MailSettings: View {
 
     var body: some View {
         Form {
+            Picker("Schriftart für Mailtexte", selection: $bodyFontName) {
+                ForEach(fontNames, id: \.self) { Text($0).tag($0) }
+            }
+            Stepper("Schriftgröße: \(Int(bodyFontSize)) pt", value: $bodyFontSize, in: 8...48)
+            Text("Vorschau Mailtext").font(.custom(bodyFontName, size: bodyFontSize))
+            Toggle("Externe Inhalte in HTML-Mails blockieren", isOn: $blockRemoteContent)
+            Text("Gilt beim Öffnen einer Mail. Inhalte können für eine einzelne Mail freigegeben werden. Eigene HTML-Schriftformate bleiben erhalten.")
+                .font(.caption).foregroundStyle(.secondary)
+            Divider()
             Toggle("Sofortempfang mit IMAP IDLE", isOn: $idleEnabled)
             Text("Neue Mails werden bei laufender App sofort gemeldet. Das Prüfintervall dient zusätzlich als Absicherung.").font(.caption).foregroundStyle(.secondary)
             Picker("Auf neue Mails prüfen", selection: $pollMinutes) {
@@ -34,6 +60,17 @@ struct MailSettings: View {
             Toggle("Beim Start automatisch auf neue Mails prüfen", isOn: $checkOnLaunch)
             Toggle("Gemeinsamen Posteingang anzeigen", isOn: $showInbox)
             Toggle("Gemeinsamen Papierkorb anzeigen", isOn: $showTrash)
+            Picker("Als gelesen markieren", selection: $markReadImmediately) {
+                Text("Sofort bei Auswahl").tag(true)
+                Text("Nach einer Wartezeit").tag(false)
+            }
+            if !markReadImmediately {
+                Stepper("Nach \(markReadDelaySeconds) Sekunden", value: $markReadDelaySeconds, in: 1...3600)
+                TextField("Wartezeit in Sekunden", value: $markReadDelaySeconds, format: .number)
+                    .onChange(of: markReadDelaySeconds) { _, value in
+                        markReadDelaySeconds = min(3600, max(1, value))
+                    }
+            }
             Picker("Beim Löschen von Mails nachfragen", selection: $deleteConfirmation) {
                 Text("Immer").tag(MailDeleteConfirmation.always)
                 Text("Nur bei mehreren Nachrichten").tag(MailDeleteConfirmation.multiple)
diff --git a/MikeMail/MailStore.swift b/MikeMail/MailStore.swift
index 4727097..8254475 100644
--- a/MikeMail/MailStore.swift
+++ b/MikeMail/MailStore.swift
@@ -1,5 +1,6 @@
 import Foundation
 import Observation
+import SwiftUI
 
 @MainActor @Observable
 final class MailStore {
@@ -130,7 +131,7 @@ final class MailStore {
         items.flatMap { [$0] + allFolders($0.children ?? []) }
     }
 
-    func refresh(folderID: String?, accountID: UUID? = nil) async {
+    func refresh(folderID: String?, accountID: UUID? = nil, inboxOnly: Bool = false) async {
         guard !isBusy else { return }
         isBusy = true
         defer { isBusy = false }
@@ -143,8 +144,8 @@ final class MailStore {
                     defer { client.close() }
                     status = "\(account.email): Verbindung wird aufgebaut …"
                     try await client.login(account: account, password: PasswordStore.password(for: account.id))
-                    var discovered = try await client.folders(accountID: account.id)
-                    let pending = try archive.pendingSent(accountID: account.id)
+                    var discovered = inboxOnly ? (folders[account.id] ?? []) : try await client.folders(accountID: account.id)
+                    let pending = inboxOnly ? [] : try archive.pendingSent(accountID: account.id)
                     if !pending.isEmpty {
                         var sent = allFolders(discovered).first { $0.specialUse?.contains("\\sent") == true }
                             ?? allFolders(discovered).first { ["sent", "gesendet", "sent messages", "sent items"].contains($0.name.lowercased()) }
@@ -175,7 +176,7 @@ final class MailStore {
                         try archive.reconcile(folderID: removed.id, inventory: MailboxInventory(validity: "", flags: [:]))
                     }
                     folders = updated
-                    for folder in allFolders(discovered) where folder.selectable {
+                    for folder in allFolders(discovered) where folder.selectable && (!inboxOnly || folder.isInbox) {
                         do {
                             status = "\(folder.name): Änderungen prüfen …"
                             let inventory = try await client.inventory(folder: folder)
@@ -229,7 +230,7 @@ final class MailStore {
         } catch { self.error = error.localizedDescription }
     }
 
-    func send(accountID: UUID?, recipients: String, cc: String = "", bcc: String = "", subject: String, body: String, attachments: [MailAttachment]) async throws {
+    func send(accountID: UUID?, recipients: String, cc: String = "", bcc: String = "", subject: String, body: String, attachments: [MailAttachment], htmlBody: String? = nil) async throws {
         guard let account = accounts.first(where: { $0.id == accountID }) else {
             throw MailError.message("Bitte ein Absenderkonto auswählen.")
         }
@@ -243,7 +244,7 @@ final class MailStore {
         let copies = Self.addresses(cc)
         let blindCopies = Self.addresses(bcc)
         let envelope = Array(Set(addresses + copies + blindCopies)).sorted()
-        let data = try MIME.compose(from: account.email, to: addresses, cc: copies, bcc: blindCopies, subject: subject, body: body, attachments: attachments)
+        let data = try MIME.compose(from: account.email, to: addresses, cc: copies, bcc: blindCopies, subject: subject, body: body, attachments: attachments, htmlBody: htmlBody)
         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.
@@ -274,8 +275,24 @@ final class MailStore {
         }
     }
 
+    var composeDrafts: [UUID: ComposeDraft] = [:]
+
+    func prepareCompose(_ draft: ComposeDraft) -> UUID {
+        composeDrafts[draft.id] = draft
+        return draft.id
+    }
+
+    func moveAccounts(from offsets: IndexSet, to destination: Int) {
+        var updated = accounts
+        updated.move(fromOffsets: offsets, toOffset: destination)
+        do {
+            try storage().saveConfiguration(ArchiveConfiguration(accounts: updated, folders: folders, recipients: recipientHistory))
+            accounts = updated
+        } catch { self.error = error.localizedDescription }
+    }
+
     func reorderAccount(_ id: UUID, before target: UUID) {
-        guard !isBusy, id != target,
+        guard id != target,
               let source = accounts.first(where: { $0.id == id }) else { return }
         var updated = accounts.filter { $0.id != id }
         guard let index = updated.firstIndex(where: { $0.id == target }) else { return }
@@ -299,20 +316,26 @@ final class MailStore {
         } catch { client.close(); throw error }
     }
 
-    /// Serializes user mutations with synchronization. Refresh also reconciles partial successes.
-    private func mutate(_ operation: () async throws -> Void) async {
+    /// Message mutations commit their confirmed changes locally; folder operations rediscover the tree.
+    private func mutate(refreshAfter: Bool = true, _ operation: () async throws -> Void) async {
         while isBusy { if Task.isCancelled { return }; try? await Task.sleep(for: .milliseconds(150)) }
+        guard !Task.isCancelled else { return }
         isBusy = true
         var failure: String?
         do { try await operation() }
         catch { failure = error.localizedDescription }
         isBusy = false
-        await refresh(folderID: selectedFolderID)
+        if refreshAfter { await refresh(folderID: selectedFolderID) }
+        else {
+            do { try updateLocalPresentation() }
+            catch { self.error = error.localizedDescription }
+            status = failure == nil ? "Änderung gespeichert." : "Änderung nicht vollständig ausgeführt."
+        }
         if let failure { error = failure }
     }
 
     func moveMessages(ids: [String], to destination: MailFolder) async {
-        await mutate {
+        await mutate(refreshAfter: false) {
             guard destination.selectable else { throw MailError.message("Bitte einen beschreibbaren Zielordner wählen.") }
             for id in Set(ids) {
                 try await self.moveOne(id: id, to: destination)
@@ -328,13 +351,16 @@ final class MailStore {
         }
         let sourceClient = try await client(for: source.accountID)
         defer { sourceClient.close() }
-        let inventory = try await sourceClient.inventory(folder: source, writable: true)
+        let inventory = try await sourceClient.messageInventory(folder: source, uid: uid)
         guard inventory.validity == record.validity, inventory.flags[uid] != nil else {
             throw MailError.message("Der Serverbestand hat sich verändert. Bitte erneut abrufen.")
         }
         let capabilities = try await sourceClient.capabilities()
         if source.accountID == destination.accountID, capabilities.contains("MOVE") {
-            try await sourceClient.move(uid: uid, to: destination.path)
+            let assigned = try await sourceClient.move(uid: uid, to: destination.path)
+            try storage().applyMessageChange(id: id, destination: destination.id, assigned: assigned, flags: inventory.flags[uid])
+            try updateLocalPresentation()
+            if assigned == nil { try await reconcileDestination(destination) }
             return
         }
         guard capabilities.contains("UIDPLUS") else {
@@ -343,25 +369,56 @@ final class MailStore {
         let raw = try await sourceClient.rawMessage(uid: uid)
         let targetClient = try await client(for: destination.accountID)
         defer { targetClient.close() }
-        try await targetClient.append(raw, path: destination.path, flags: inventory.flags[uid] ?? [])
+        let assigned = try await targetClient.append(raw, path: destination.path, flags: inventory.flags[uid] ?? [])
         // A positive tagged APPEND completion precedes any source deletion.
+        // Record the confirmed copy even if removing the source later fails.
+        if let assigned {
+            try storage().store(raw: raw, folderID: destination.id, validity: assigned.validity,
+                uid: assigned.uid, flags: inventory.flags[uid] ?? [])
+        } else { try await reconcileDestination(destination) }
         do { try await sourceClient.remove(uids: [uid]) }
         catch {
             throw MailError.message("Die Nachricht wurde ins Ziel kopiert, konnte aber nicht aus der Quelle entfernt werden. Beide Kopien bleiben erhalten. \(error.localizedDescription)")
         }
+        try storage().applyMessageChange(id: id)
+        try updateLocalPresentation()
+    }
+
+    private func updateLocalPresentation() throws {
+        unreadCounts = try storage().unreadCounts()
+        archiveRevision += 1
+        if let selectedFolderID { try display(folderID: selectedFolderID) }
+    }
+
+    /// Servers without COPYUID/APPENDUID need only the destination folder reconciled.
+    private func reconcileDestination(_ folder: MailFolder) async throws {
+        let archive = try storage()
+        let client = try await client(for: folder.accountID)
+        defer { client.close() }
+        let inventory = try await client.inventory(folder: folder)
+        let known = try archive.knownUIDs(folderID: folder.id, validity: inventory.validity)
+        for uid in Set(inventory.flags.keys).subtracting(known) {
+            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)
+        try updateLocalPresentation()
     }
 
     func deleteMessages(ids: [String]) async {
-        await mutate {
+        await mutate(refreshAfter: false) {
             for id in Set(ids) {
                 let record = try self.storage().record(id: id)
                 guard let source = self.folder(id: record.folderID), let uid = UInt64(record.uid) else { continue }
                 if source.isTrash {
                     let client = try await self.client(for: source.accountID)
                     defer { client.close() }
-                    let inventory = try await client.inventory(folder: source, writable: true)
+                    let inventory = try await client.messageInventory(folder: source, uid: uid)
                     guard inventory.validity == record.validity else { throw MailError.message("Ordnerbestand geändert. Bitte erneut abrufen.") }
                     try await client.remove(uids: inventory.flags[uid] == nil ? [] : [uid])
+                    try self.storage().applyMessageChange(id: id)
+                    try self.updateLocalPresentation()
                 } else {
                     guard let trash = self.allFolders(self.folders[source.accountID] ?? []).first(where: \.isTrash) else {
                         throw MailError.message("Für dieses Konto wurde kein Papierkorb gefunden. Bitte zuerst einen Ordner „Trash“ erstellen.")
@@ -456,17 +513,21 @@ final class MailStore {
     }
 
     func setRead(ids: [String], read: Bool) async {
-        await mutate {
+        await mutate(refreshAfter: false) {
             for id in Set(ids) {
                 let record = try self.storage().record(id: id)
                 guard let folder = self.folder(id: record.folderID), let uid = UInt64(record.uid) else { continue }
                 let client = try await self.client(for: folder.accountID)
                 defer { client.close() }
-                let inventory = try await client.inventory(folder: folder, writable: true)
+                let inventory = try await client.messageInventory(folder: folder, uid: uid)
                 guard inventory.validity == record.validity, inventory.flags[uid] != nil else {
                     throw MailError.message("Nachricht wurde auf dem Server verändert. Bitte erneut abrufen.")
                 }
                 try await client.setSeen(uid: uid, read: read)
+                var flags = (inventory.flags[uid] ?? []).filter { $0.lowercased() != "\\seen" }
+                if read { flags.append("\\Seen") }
+                try self.storage().applyMessageChange(id: id, flags: flags, removed: false)
+                try self.updateLocalPresentation()
             }
         }
     }
@@ -517,7 +578,7 @@ final class MailStore {
                 guard let id = self.pendingIdleAccounts.first else { return }
                 self.pendingIdleAccounts.remove(id)
                 guard self.accounts.contains(where: { $0.id == id }) else { continue }
-                await self.refresh(folderID: self.selectedFolderID, accountID: id)
+                await self.refresh(folderID: self.selectedFolderID, accountID: id, inboxOnly: true)
             }
         }
     }
diff --git a/MikeMail/MessageActions.swift b/MikeMail/MessageActions.swift
index 95508dd..1af3f44 100644
--- a/MikeMail/MessageActions.swift
+++ b/MikeMail/MessageActions.swift
@@ -40,9 +40,11 @@ struct MessageActionButtons: View {
 struct MessageDetailWindow: View {
     let store: MailStore
     let messageID: String?
-    @State private var draft: ComposeDraft?
+    @Environment(\.openWindow) private var openWindow
     @State private var confirmingDelete = false
     @AppStorage("mailDeleteConfirmation") private var deleteConfirmation: MailDeleteConfirmation = .always
+    @AppStorage("markReadImmediately") private var markReadImmediately = false
+    @AppStorage("markReadDelaySeconds") private var markReadDelaySeconds = 1
 
     private var message: MailMessage? {
         _ = store.archiveRevision
@@ -57,15 +59,15 @@ struct MessageDetailWindow: View {
                     guard let message else { return }
                     switch command {
                     case .reply, .forward:
-                        draft = .from(message, accountID: store.accountID(for: message.id), forwarding: command == .forward)
+                        let draft = ComposeDraft.from(message, accountID: store.accountID(for: message.id), forwarding: command == .forward)
+                        openWindow(id: "compose", value: store.prepareCompose(draft))
                     case .delete:
                         if deleteConfirmation.isRequired(count: 1) { confirmingDelete = true }
                         else { Task { await store.deleteMessages(ids: [message.id]) } }
                     default: break
                     }
-                }.disabled(message == nil || store.isBusy)
+                }.disabled(message == nil)
             }
-            .sheet(item: $draft) { ComposeView(store: store, draft: $0) }
             .alert("Nachricht löschen?", isPresented: $confirmingDelete) {
                 Button("Abbrechen", role: .cancel) {}
                 Button("Löschen", role: .destructive) {
@@ -76,8 +78,12 @@ struct MessageDetailWindow: View {
                     ? "Die Nachricht wird auch auf dem Server endgültig gelöscht."
                     : "Die Nachricht wird auch auf dem Server in den Papierkorb verschoben.")
             }
-            .task(id: messageID) {
-                if let message, !message.isRead { await store.setRead(ids: [message.id], read: true) }
+            .task(id: AutoReadRequest(ids: Set([messageID].compactMap { $0 }), immediately: markReadImmediately, seconds: markReadDelaySeconds)) {
+                guard let message, !message.isRead else { return }
+                do {
+                    try await AutoReadRequest(ids: [message.id], immediately: markReadImmediately, seconds: markReadDelaySeconds).wait()
+                    await store.setRead(ids: [message.id], read: true)
+                } catch { /* The message window closed before the read delay elapsed. */ }
             }
             .alert("MikeMail", isPresented: Binding(get: { store.error != nil }, set: { if !$0 { store.error = nil } })) {
                 Button("OK") { store.error = nil }
diff --git a/MikeMail/MikeMailApp.swift b/MikeMail/MikeMailApp.swift
index 13f547b..65205b0 100644
--- a/MikeMail/MikeMailApp.swift
+++ b/MikeMail/MikeMailApp.swift
@@ -17,6 +17,13 @@ struct MikeMailApp: App {
         WindowGroup("Nachricht", id: "message", for: String.self) { $id in
             MessageDetailWindow(store: store, messageID: id)
         }.defaultSize(width: 800, height: 650)
+        .windowResizability(.contentMinSize)
+        WindowGroup("Neue Nachricht", id: "compose", for: UUID.self) { $id in
+            ComposeView(store: store, draft: id.flatMap { store.composeDrafts[$0] })
+                .onDisappear { if let id { store.composeDrafts.removeValue(forKey: id) } }
+        }
+        .defaultSize(width: 760, height: 780)
+        .windowResizability(.contentMinSize)
         Settings { MailSettings() }
     }
 }
diff --git a/MikeMail/UITestFixture.swift b/MikeMail/UITestFixture.swift
index 8da73fa..1ff66be 100644
--- a/MikeMail/UITestFixture.swift
+++ b/MikeMail/UITestFixture.swift
@@ -9,14 +9,17 @@ extension MailStore {
             let archive = try MailArchive(root: root)
             let account = MailAccount(name: "UI-Prüfung", email: "fixture@example.com", username: "fixture", host: "example.invalid")
             let inbox = MailFolder(accountID: account.id, path: "INBOX", name: "Posteingang")
-            try archive.saveConfiguration(ArchiveConfiguration(accounts: [account], folders: [account.id: [inbox]], recipients: []))
+            let second = MailAccount(name: "Zweites Testkonto", email: "second@example.com", username: "second", host: "example.invalid")
+            try archive.saveConfiguration(ArchiveConfiguration(accounts: [account, second], folders: [account.id: [inbox], second.id: []], recipients: []))
             for index in 1...2 {
                 let raw = try MIME.compose(from: "sender@example.com", to: [account.email],
                     subject: "UI-Nachricht \(index)", body: "Nachrichtentext für die Fensterprüfung.",
                     attachments: [MailAttachment(name: "Beispiel.txt", mimeType: "text/plain", data: Data("Anhang".utf8))])
                 try archive.store(raw: raw, folderID: inbox.id, validity: "1", uid: "\(index)", flags: ["\\Seen"])
             }
-            return MailStore(archive: archive)
+            let store = MailStore(archive: archive)
+            if ProcessInfo.processInfo.arguments.contains("--ui-busy") { store.isBusy = true }
+            return store
         } catch { fatalError("UI fixture: \(error)") }
     }
 }
diff --git a/MikeMailTests/MailArchiveTests.swift b/MikeMailTests/MailArchiveTests.swift
index e3c0371..8540329 100644
--- a/MikeMailTests/MailArchiveTests.swift
+++ b/MikeMailTests/MailArchiveTests.swift
@@ -4,6 +4,51 @@ import Testing
 
 @MainActor
 struct MailArchiveTests {
+    @Test func confirmedMessageChangesPreserveOtherMailAndBackup() throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let archive = try MailArchive(root: root.appending(path: "Archive"))
+        let account = MailAccount(name: "Fixture", email: "fixture@example.com", username: "fixture", host: "example.invalid")
+        let inbox = MailFolder(accountID: account.id, path: "INBOX", name: "Posteingang")
+        let trash = MailFolder(accountID: account.id, path: "Trash", name: "Papierkorb")
+        try archive.saveConfiguration(ArchiveConfiguration(accounts: [account], folders: [account.id: [inbox, trash]], recipients: []))
+        let raw = Data("Subject: Move\r\n\r\nBody".utf8)
+        for uid in ["1", "2"] { try archive.store(raw: raw, folderID: inbox.id, validity: "10", uid: uid, flags: []) }
+        let id = inbox.id + ":10:1"
+        try archive.applyMessageChange(id: id, flags: ["\\Seen"], removed: false)
+        #expect(try archive.message(id: id).isRead)
+        try archive.applyMessageChange(id: id, destination: trash.id, assigned: .init(validity: "20", uid: "9"), flags: ["\\Seen"])
+        #expect(try archive.messages(folderID: inbox.id).map(\.id) == [inbox.id + ":10:2"])
+        #expect(try archive.message(id: trash.id + ":20:9").body == "Body")
+        #expect(try archive.unreadCounts()[inbox.id] == 1)
+        try archive.applyMessageChange(id: trash.id + ":20:9")
+        #expect(try archive.messages(folderID: trash.id).isEmpty)
+        let backup = root.appending(path: "Backup")
+        try archive.exportSnapshot(to: backup)
+        let restored = try MailArchive.restoreSnapshot(from: backup, to: root.appending(path: "Restored"))
+        #expect(try restored.messages(folderID: trash.id).isEmpty)
+        #expect(try restored.messages(folderID: inbox.id).count == 1)
+    }
+
+    @Test func singleMessageServerUIDMapping() {
+        #expect(IMAPClient.assignedUID(["M1 OK [COPYUID 123 5 17] Done"], sourceUID: 5) == .init(validity: "123", uid: "17"))
+        #expect(IMAPClient.assignedUID(["* OK [COPYUID 123 5 17] Done"], sourceUID: 6) == nil)
+        #expect(IMAPClient.assignedUID(["M2 OK [APPENDUID 123 18] Done"]) == .init(validity: "123", uid: "18"))
+        #expect(IMAPClient.assignedUID(["M2 OK Done"]) == nil)
+        #expect(IMAPClient.assignedUID(["M2 OK [APPENDUID 0 18] Done"]) == nil)
+        #expect(IMAPClient.assignedUID(["M2 OK [COPYUID 123 5:6 17:18] Done"], sourceUID: 5) == nil)
+    }
+
+    @Test func automaticReadDelayIsCancellable() async throws {
+        try await AutoReadRequest(ids: ["mail"], immediately: true, seconds: 3600).wait()
+        let delayed = Task { try await AutoReadRequest(ids: ["mail"], immediately: false, seconds: 3600).wait() }
+        delayed.cancel()
+        do {
+            try await delayed.value
+            Issue.record("Cancelled selection must not be marked as read")
+        } catch is CancellationError { }
+    }
+
     @Test func diskPersistenceIncrementalReconciliationAndRestore() throws {
         let base = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
         defer { try? FileManager.default.removeItem(at: base) }
diff --git a/MikeMailTests/MailPresentationTests.swift b/MikeMailTests/MailPresentationTests.swift
new file mode 100644
index 0000000..1edbaa6
--- /dev/null
+++ b/MikeMailTests/MailPresentationTests.swift
@@ -0,0 +1,104 @@
+import Foundation
+import AppKit
+import WebKit
+import Testing
+@testable import MikeMail
+
+@MainActor
+struct MailPresentationTests {
+    @Test func htmlAlternativeAndAttachmentsSurviveArchive() throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let html = "<p style=\"font-family: Georgia; color: #ff0000; font-size: 24px\"><b>Grüße</b> <i>Welt</i></p>"
+        let bytes = Data([0, 1, 254, 255])
+        let raw = try MIME.compose(from: "from@example.com", to: ["to@example.com"], subject: "HTML",
+            body: "Grüße Welt", attachments: [MailAttachment(name: "Probe.bin", mimeType: "application/octet-stream", data: bytes)],
+            htmlBody: html)
+        let archive = try MailArchive(root: root)
+        try archive.store(raw: raw, folderID: "inbox", validity: "1", uid: "1", flags: [])
+        let message = try #require(archive.messages(folderID: "inbox").first)
+        #expect(message.body == "Grüße Welt")
+        #expect(message.htmlBody == html)
+        #expect(message.attachments.first?.data == bytes)
+        let htmlOnly = MIME.parse(Data("Content-Type: text/html; charset=utf-8\r\n\r\n<p><b>Hallo</b> Welt</p>".utf8), id: "html")
+        #expect(htmlOnly.htmlBody?.contains("<b>Hallo</b>") == true)
+        #expect(htmlOnly.body.contains("Hallo Welt"))
+    }
+
+    @Test func selectedFormattingExportsHTMLWithoutChangingOtherText() throws {
+        let editor = MailEditorModel()
+        let view = NSTextView()
+        view.string = "Hallo Welt"
+        view.font = NSFont(name: "Helvetica", size: 14)
+        editor.textView = view
+        view.setSelectedRange(NSRange(location: 0, length: 5))
+        editor.toggleTrait(.boldFontMask, enabled: true)
+        editor.setAttribute(.foregroundColor, value: NSColor(srgbRed: 1, green: 0, blue: 0, alpha: 1))
+        editor.setFont(size: 24)
+        let selected = try #require(view.textStorage?.attribute(.font, at: 0, effectiveRange: nil) as? NSFont)
+        let remaining = try #require(view.textStorage?.attribute(.font, at: 6, effectiveRange: nil) as? NSFont)
+        #expect(NSFontManager.shared.traits(of: selected).contains(.boldFontMask))
+        #expect(selected.pointSize == 24)
+        #expect(remaining.pointSize == 14)
+        let html = try editor.html()
+        #expect(html.contains("24"))
+        // Cocoa's HTML writer converts color profiles, so compare the exported color with tolerance.
+        let colorRange = try #require(html.range(of: "#[0-9a-fA-F]{6}", options: .regularExpression))
+        let rgb = try #require(UInt32(html[colorRange].dropFirst(), radix: 16))
+        #expect((rgb >> 16) > 230 && ((rgb >> 8) & 255) < 25 && (rgb & 255) < 25)
+        #expect(editor.plainText == "Hallo Welt")
+    }
+
+    @Test func accountOrderPersistsInBothDirections() throws {
+        let root = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: root) }
+        let archive = try MailArchive(root: root)
+        let accounts = ["A", "B", "C"].map { MailAccount(name: $0) }
+        try archive.saveConfiguration(ArchiveConfiguration(accounts: accounts, folders: [:], recipients: []))
+        let store = MailStore(archive: archive)
+        store.moveAccounts(from: IndexSet(integer: 0), to: 3)
+        #expect(store.accounts.map(\.name) == ["B", "C", "A"])
+        #expect(try MailArchive(root: root).configuration()?.accounts.map(\.name) == ["B", "C", "A"])
+        store.moveAccounts(from: IndexSet(integer: 2), to: 0)
+        #expect(store.accounts == accounts)
+        #expect(try archive.configuration()?.accounts == accounts)
+    }
+
+    @Test func senderAndDatePresentation() throws {
+        #expect(MailDisplay.sender("\"Max Muster\" <max@example.com>") == "Max Muster <max@example.com>")
+        #expect(MailDisplay.sender("max@example.com") == "max@example.com")
+        let date = try #require(ISO8601DateFormatter().date(from: "2026-11-07T15:04:00Z"))
+        #expect(MailDisplay.date(date, timeZone: try #require(TimeZone(secondsFromGMT: 0))) == "07.11.2026 15:04")
+    }
+
+    @Test func htmlRendererBlocksRemoteResourcesAndScripts() async throws {
+        let config = WKWebViewConfiguration()
+        config.websiteDataStore = .nonPersistent()
+        config.defaultWebpagePreferences.allowsContentJavaScript = false
+        // An application-owned script records CSP violations without allowing mail scripts.
+        config.userContentController.addUserScript(WKUserScript(source: """
+            window.blockedResources = [];
+            document.addEventListener('securitypolicyviolation', e => window.blockedResources.push(e.blockedURI));
+            """, injectionTime: .atDocumentStart, forMainFrameOnly: true))
+        let view = WKWebView(frame: NSRect(x: 0, y: 0, width: 600, height: 400), configuration: config)
+        let html = """
+            <p id="styled" style="color: rgb(255, 0, 0); font-size:24px"><b>HTML</b></p>
+            <img src="https://example.invalid/tracker.png">
+            <style>body { background-image:url(https://example.invalid/background.png) }</style>
+            <script>window.mailScriptRan = true;</script>
+            """
+        view.loadHTMLString(MailHTML.document(html, attachments: [], blocked: true, font: "Helvetica", size: 14), baseURL: nil)
+        var violations: [String] = []
+        for _ in 0..<100 {
+            try await Task.sleep(for: .milliseconds(50))
+            violations = (try? await view.evaluateJavaScript("window.blockedResources")) as? [String] ?? []
+            if violations.contains(where: { $0.contains("tracker.png") }) { break }
+        }
+        #expect(violations.contains { $0.contains("tracker.png") })
+        #expect(violations.contains { $0.contains("background.png") })
+        let style = try await view.evaluateJavaScript("getComputedStyle(document.getElementById('styled')).color") as? String
+        #expect(style == "rgb(255, 0, 0)")
+        let scriptRan = try await view.evaluateJavaScript("window.mailScriptRan === true") as? Bool
+        #expect(scriptRan == false)
+    }
+}
diff --git a/MikeMailUITests/MikeMailUITests.swift b/MikeMailUITests/MikeMailUITests.swift
index 45b660e..2e7d687 100644
--- a/MikeMailUITests/MikeMailUITests.swift
+++ b/MikeMailUITests/MikeMailUITests.swift
@@ -49,7 +49,7 @@ final class MikeMailUITests: XCTestCase {
             app.menuItems["New"].hover()
             app.menuItems["New Window"].click()
         }
-        let table = app.outlines.element(boundBy: 1)
+        let table = app.outlines.firstMatch
         XCTAssertTrue(table.waitForExistence(timeout: 5), app.debugDescription)
         let row = table.descendants(matching: .outlineRow).firstMatch
         XCTAssertTrue(row.waitForExistence(timeout: 5), app.debugDescription)
@@ -62,6 +62,83 @@ final class MikeMailUITests: XCTestCase {
         XCTAssertGreaterThanOrEqual(app.windows.count, 2, app.debugDescription)
         reply.click()
         XCTAssertTrue(app.textFields["composeCC"].waitForExistence(timeout: 5))
-        app.buttons["Abbrechen"].click()
+        let compose = app.windows["Neue Nachricht"].firstMatch
+        XCTAssertTrue(compose.waitForExistence(timeout: 5))
+        XCTAssertGreaterThanOrEqual(app.windows.count, 3)
+        let body = compose.textViews["composeBody"]
+        XCTAssertTrue(body.waitForExistence(timeout: 5))
+        app.typeText("Antwort am Anfang ")
+        XCTAssertTrue((body.value as? String ?? "").hasPrefix("Antwort am Anfang "))
+        let oldFrame = compose.frame
+        resizeWindow(compose, app: app)
+        XCTAssertNotEqual(compose.frame.size, oldFrame.size)
+        compose.buttons["Abbrechen"].click()
+        let oldDetail = detail.frame
+        detail.coordinate(withNormalizedOffset: CGVector(dx: 0.5, dy: 0.01)).click()
+        resizeWindow(detail, app: app)
+        XCTAssertNotEqual(detail.frame.size, oldDetail.size)
+    }
+
+    @MainActor
+    func testDeleteConfirmation() {
+        let app = XCUIApplication()
+        app.launchArguments = ["-ApplePersistenceIgnoreState", "YES", "--ui-fixture", "-checkOnLaunch", "NO",
+            "-idleEnabled", "NO", "-pollMinutes", "0", "-selectedFolder", "unified:inbox", "-mailSearch", "",
+            "-mailDeleteConfirmation", "always", "--ui-busy"]
+        app.launch()
+        app.activate()
+        if app.windows.count == 0 {
+            app.menuBars.menuBarItems["File"].click()
+            app.menuItems["New"].hover()
+            app.menuItems["New Window"].click()
+        }
+        let table = app.outlines.firstMatch
+        XCTAssertTrue(table.waitForExistence(timeout: 5))
+        table.staticTexts["UI-Nachricht 1"].firstMatch.click()
+        app.buttons["Löschen…"].firstMatch.click()
+        XCTAssertTrue(app.buttons["Abbrechen"].waitForExistence(timeout: 3), app.debugDescription)
+        if app.buttons["Abbrechen"].exists { app.buttons["Abbrechen"].click() }
+    }
+
+    @MainActor
+    func testAccountReorderingAndDisclosure() {
+        continueAfterFailure = false
+        let app = XCUIApplication()
+        app.launchArguments = ["-ApplePersistenceIgnoreState", "YES", "--ui-fixture", "-checkOnLaunch", "NO",
+            "-idleEnabled", "NO", "-pollMinutes", "0", "-selectedFolder", "unified:inbox", "-mailSearch", ""]
+        app.launch()
+        app.activate()
+        if app.windows.count == 0 {
+            app.menuBars.menuBarItems["File"].click()
+            app.menuItems["New"].hover()
+            app.menuItems["New Window"].click()
+        }
+        app.activate()
+        let sidebar = app.tables["accountSidebar"]
+        XCTAssertTrue(sidebar.waitForExistence(timeout: 5))
+        let rows = sidebar.tableRows
+        XCTAssertTrue(rows.element(boundBy: 4).waitForExistence(timeout: 5))
+        let source = rows.element(boundBy: 4)
+        let target = rows.element(boundBy: 2)
+        let disclosure = target.buttons.firstMatch
+        XCTAssertTrue(disclosure.exists)
+        XCTAssertEqual(disclosure.frame.midY, target.frame.midY, accuracy: 2)
+        source.staticTexts["Zweites Testkonto"].click(forDuration: 1, thenDragTo: target.staticTexts["UI-Prüfung"])
+        XCTAssertTrue(rows.element(boundBy: 2).debugDescription.contains("second@example.com"), sidebar.debugDescription)
+    }
+
+    @MainActor
+    private func resizeWindow(_ window: XCUIElement, app: XCUIApplication) {
+        let original = window.frame.size
+        app.menuBars.menuBarItems["Window"].click()
+        app.menuItems["Fill"].click()
+        if window.frame.size == original {
+            app.menuBars.menuBarItems["Window"].click()
+            app.menuItems["Move & Resize"].hover()
+            app.menuItems["Left"].click()
+        }
+        let changed = NSPredicate { _, _ in window.frame.size != original }
+        expectation(for: changed, evaluatedWith: window)
+        waitForExpectations(timeout: 3)
     }
 }