feat(imap): 补充邮件 IMAP 元数据支持

- 为文件夹和消息增加 `UID/ModSeq` 字段，并在迁移时回填与建索引。
- 让收发、移动、标记、删除、草稿等流程同步维护 `imap_uid` 和 `imap_modseq`。
- 扩展后端与前端类型，并补充相关测试覆盖。

apps/api/internal/app/admin_handlers.go

@@ -786,7 +786,7 @@ func (a *App) handleAdminMessages(w http.ResponseWriter, r *http.Request) {
 	}
 	args = append(args, limit+1, offset)
 
-	rows, err := a.db.QueryContext(r.Context(), `SELECT m.id,COALESCE(m.mailbox_id,''),COALESCE(mb.address,''),COALESCE(u.email,''),COALESCE(m.recipient_addr,''),COALESCE(m.folder_id,''),COALESCE(f.name,'Unregistered'),m.message_uid,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
+	rows, err := a.db.QueryContext(r.Context(), `SELECT m.id,COALESCE(m.mailbox_id,''),COALESCE(mb.address,''),COALESCE(u.email,''),COALESCE(m.recipient_addr,''),COALESCE(m.folder_id,''),COALESCE(f.name,'Unregistered'),m.message_uid,m.imap_uid,m.imap_modseq,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
 		FROM messages m
 		LEFT JOIN folders f ON f.id=m.folder_id
 		LEFT JOIN mailboxes mb ON mb.id=m.mailbox_id
@@ -1039,6 +1039,6 @@ func (a *App) ensureFolder(ctx context.Context, mailboxID, folder string) (strin
 	}
 	role := strings.ToLower(folder)
 	id = newID("fld")
-	_, err := a.db.ExecContext(ctx, `INSERT INTO folders(id,mailbox_id,name,role,created_at) VALUES(?,?,?,?,?)`, id, mailboxID, folder, role, a.now().UTC().Format(time.RFC3339Nano))
+	_, err := a.db.ExecContext(ctx, `INSERT INTO folders(id,mailbox_id,name,role,uid_validity,uid_next,highest_modseq,created_at) VALUES(?,?,?,?,?,?,?,?)`, id, mailboxID, folder, role, a.newUIDValidity(), 1, 1, a.now().UTC().Format(time.RFC3339Nano))
 	return id, err
 }

apps/api/internal/app/app.go

@@ -202,6 +202,9 @@ func (a *App) migrate(ctx context.Context) error {
 			mailbox_id TEXT NOT NULL REFERENCES mailboxes(id) ON DELETE CASCADE,
 			name TEXT NOT NULL,
 			role TEXT NOT NULL,
+			uid_validity INTEGER NOT NULL DEFAULT 0,
+			uid_next INTEGER NOT NULL DEFAULT 1,
+			highest_modseq INTEGER NOT NULL DEFAULT 1,
 			created_at TEXT NOT NULL,
 			UNIQUE(mailbox_id, name)
 		)`,
@@ -228,6 +231,8 @@ func (a *App) migrate(ctx context.Context) error {
 			has_attachments INTEGER NOT NULL DEFAULT 0,
 			size_bytes INTEGER NOT NULL DEFAULT 0,
 			raw_path TEXT NOT NULL DEFAULT '',
+			imap_uid INTEGER NOT NULL DEFAULT 0,
+			imap_modseq INTEGER NOT NULL DEFAULT 1,
 			created_at TEXT NOT NULL,
 			updated_at TEXT NOT NULL
 		)`,
@@ -429,6 +434,9 @@ func (a *App) migrate(ctx context.Context) error {
 	if err := a.migrateSendQueueMessageID(ctx); err != nil {
 		return err
 	}
+	if err := a.migrateIMAPMetadata(ctx); err != nil {
+		return err
+	}
 	if err := a.ensureDefaultPermissionGroups(ctx); err != nil {
 		return err
 	}
@@ -1030,7 +1038,7 @@ func (a *App) createMailboxWithPasswordHash(ctx context.Context, userID, domainI
 		return "", err
 	}
 	for _, f := range defaultFolderDefs() {
-		_, err = tx.ExecContext(ctx, `INSERT INTO folders(id,mailbox_id,name,role,created_at) VALUES(?,?,?,?,?)`, newID("fld"), id, f.name, f.role, now)
+		_, err = tx.ExecContext(ctx, `INSERT INTO folders(id,mailbox_id,name,role,uid_validity,uid_next,highest_modseq,created_at) VALUES(?,?,?,?,?,?,?,?)`, newID("fld"), id, f.name, f.role, a.newUIDValidity(), 1, 1, now)
 		if err != nil {
 			return "", err
 		}

apps/api/internal/app/app_test.go

@@ -2729,6 +2729,99 @@ func TestMessageFlagsUpdateMaildir(t *testing.T) {
 	}
 }
 
+func TestIMAPUIDAndModSeqProgression(t *testing.T) {
+	a := newTestApp(t)
+	ctx := context.Background()
+	a.cfg.MaildirRoot = t.TempDir()
+	srv := httptest.NewServer(a.Router())
+	defer srv.Close()
+	client := &testClient{t: t, server: srv}
+	var login map[string]any
+	if code := client.do("POST", "/api/auth/login", map[string]string{"email": "admin@lanqin.local", "password": "ChangeMe123!"}, &login); code != http.StatusOK {
+		t.Fatalf("login code=%d body=%v", code, login)
+	}
+	user, mb := defaultAdminUserAndMailbox(t, a)
+	clearMailboxMessagesForTest(t, a, mb.ID)
+	sentID, err := a.ensureFolder(ctx, mb.ID, "Sent")
+	if err != nil {
+		t.Fatal(err)
+	}
+	archiveID, err := a.ensureFolder(ctx, mb.ID, "Archive")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	first, err := a.sendMailNow(ctx, user, mb, mailComposeInput{MailboxID: mb.ID, To: []string{"one@example.test"}, Subject: "uid one", Text: "one", HTML: "<p>one</p>"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	second, err := a.sendMailNow(ctx, user, mb, mailComposeInput{MailboxID: mb.ID, To: []string{"two@example.test"}, Subject: "uid two", Text: "two", HTML: "<p>two</p>"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var firstUID, firstModSeq, secondUID int64
+	if err := a.db.QueryRowContext(ctx, `SELECT imap_uid,imap_modseq FROM messages WHERE id=?`, first.ID).Scan(&firstUID, &firstModSeq); err != nil {
+		t.Fatal(err)
+	}
+	if err := a.db.QueryRowContext(ctx, `SELECT imap_uid FROM messages WHERE id=?`, second.ID).Scan(&secondUID); err != nil {
+		t.Fatal(err)
+	}
+	if firstUID <= 0 || secondUID != firstUID+1 {
+		t.Fatalf("sent UIDs first=%d second=%d, want consecutive positive", firstUID, secondUID)
+	}
+	var sentUIDNext int64
+	if err := a.db.QueryRowContext(ctx, `SELECT uid_next FROM folders WHERE id=?`, sentID).Scan(&sentUIDNext); err != nil {
+		t.Fatal(err)
+	}
+	if sentUIDNext <= secondUID {
+		t.Fatalf("sent uid_next=%d, second uid=%d", sentUIDNext, secondUID)
+	}
+
+	starred := true
+	if err := a.updateMessageMaildirFlags(ctx, first.ID, nil, &starred); err != nil {
+		t.Fatal(err)
+	}
+	modSeq, err := a.updateMessageModSeq(ctx, first.ID, sentID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := a.db.ExecContext(ctx, `UPDATE messages SET is_starred=1,imap_modseq=? WHERE id=?`, modSeq, first.ID); err != nil {
+		t.Fatal(err)
+	}
+	var afterFlagUID, afterFlagModSeq int64
+	if err := a.db.QueryRowContext(ctx, `SELECT imap_uid,imap_modseq FROM messages WHERE id=?`, first.ID).Scan(&afterFlagUID, &afterFlagModSeq); err != nil {
+		t.Fatal(err)
+	}
+	if afterFlagUID != firstUID || afterFlagModSeq <= firstModSeq {
+		t.Fatalf("after flag uid/modseq=%d/%d, want uid %d and modseq > %d", afterFlagUID, afterFlagModSeq, firstUID, firstModSeq)
+	}
+
+	if err := a.moveMessageMaildir(ctx, first.ID, archiveID); err != nil {
+		t.Fatal(err)
+	}
+	var archiveUID, archiveModSeq int64
+	var folderID string
+	if err := a.db.QueryRowContext(ctx, `SELECT folder_id,imap_uid,imap_modseq FROM messages WHERE id=?`, first.ID).Scan(&folderID, &archiveUID, &archiveModSeq); err != nil {
+		t.Fatal(err)
+	}
+	if folderID != archiveID {
+		t.Fatalf("folder after move=%s, want archive %s", folderID, archiveID)
+	}
+	if archiveUID <= 0 {
+		t.Fatalf("archive uid=%d, want positive uid", archiveUID)
+	}
+	var archiveUIDNext, archiveHighestModSeq int64
+	if err := a.db.QueryRowContext(ctx, `SELECT uid_next,highest_modseq FROM folders WHERE id=?`, archiveID).Scan(&archiveUIDNext, &archiveHighestModSeq); err != nil {
+		t.Fatal(err)
+	}
+	if archiveUIDNext <= archiveUID {
+		t.Fatalf("archive uid_next=%d, uid=%d", archiveUIDNext, archiveUID)
+	}
+	if archiveModSeq != archiveHighestModSeq {
+		t.Fatalf("archive modseq=%d highest=%d, want equal", archiveModSeq, archiveHighestModSeq)
+	}
+}
+
 func TestMaildirSyncUpdatesMovedMessageState(t *testing.T) {
 	a := newTestApp(t)
 	ctx := context.Background()

apps/api/internal/app/imap_metadata.go

@@ -0,0 +1,242 @@
+package app
+
+import (
+	"context"
+	"database/sql"
+	"math"
+	"time"
+)
+
+type imapMetadata struct {
+	UID    int64
+	ModSeq int64
+}
+
+func (a *App) migrateIMAPMetadata(ctx context.Context) error {
+	if err := a.ensureTableColumn(ctx, "folders", "uid_validity", `ALTER TABLE folders ADD COLUMN uid_validity INTEGER NOT NULL DEFAULT 0`); err != nil {
+		return err
+	}
+	if err := a.ensureTableColumn(ctx, "folders", "uid_next", `ALTER TABLE folders ADD COLUMN uid_next INTEGER NOT NULL DEFAULT 1`); err != nil {
+		return err
+	}
+	if err := a.ensureTableColumn(ctx, "folders", "highest_modseq", `ALTER TABLE folders ADD COLUMN highest_modseq INTEGER NOT NULL DEFAULT 1`); err != nil {
+		return err
+	}
+	if err := a.ensureTableColumn(ctx, "messages", "imap_uid", `ALTER TABLE messages ADD COLUMN imap_uid INTEGER NOT NULL DEFAULT 0`); err != nil {
+		return err
+	}
+	if err := a.ensureTableColumn(ctx, "messages", "imap_modseq", `ALTER TABLE messages ADD COLUMN imap_modseq INTEGER NOT NULL DEFAULT 1`); err != nil {
+		return err
+	}
+	if _, err := a.db.ExecContext(ctx, `UPDATE folders SET uid_validity=? WHERE uid_validity=0`, a.newUIDValidity()); err != nil {
+		return err
+	}
+	if _, err := a.db.ExecContext(ctx, `UPDATE folders SET uid_next=1 WHERE uid_next<1`); err != nil {
+		return err
+	}
+	if _, err := a.db.ExecContext(ctx, `UPDATE folders SET highest_modseq=1 WHERE highest_modseq<1`); err != nil {
+		return err
+	}
+	if err := a.backfillIMAPUIDs(ctx); err != nil {
+		return err
+	}
+	_, err := a.db.ExecContext(ctx, `CREATE UNIQUE INDEX IF NOT EXISTS idx_messages_folder_imap_uid ON messages(folder_id, imap_uid) WHERE folder_id IS NOT NULL AND imap_uid > 0`)
+	return err
+}
+
+func (a *App) ensureTableColumn(ctx context.Context, table, column, alterSQL string) error {
+	rows, err := a.db.QueryContext(ctx, `PRAGMA table_info(`+table+`)`)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var cid int
+		var name, typ string
+		var notNull int
+		var dflt any
+		var pk int
+		if err := rows.Scan(&cid, &name, &typ, &notNull, &dflt, &pk); err != nil {
+			return err
+		}
+		if name == column {
+			return nil
+		}
+	}
+	if err := rows.Err(); err != nil {
+		return err
+	}
+	_, err = a.db.ExecContext(ctx, alterSQL)
+	return err
+}
+
+func (a *App) backfillIMAPUIDs(ctx context.Context) error {
+	rows, err := a.db.QueryContext(ctx, `SELECT id FROM folders ORDER BY created_at,id`)
+	if err != nil {
+		return err
+	}
+	var folderIDs []string
+	for rows.Next() {
+		var folderID string
+		if err := rows.Scan(&folderID); err != nil {
+			rows.Close()
+			return err
+		}
+		folderIDs = append(folderIDs, folderID)
+	}
+	if err := rows.Err(); err != nil {
+		rows.Close()
+		return err
+	}
+	if err := rows.Close(); err != nil {
+		return err
+	}
+	for _, folderID := range folderIDs {
+		if err := a.backfillFolderIMAPUIDs(ctx, folderID); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (a *App) backfillFolderIMAPUIDs(ctx context.Context, folderID string) error {
+	rows, err := a.db.QueryContext(ctx, `SELECT id FROM messages WHERE folder_id=? AND imap_uid=0 ORDER BY created_at,id`, folderID)
+	if err != nil {
+		return err
+	}
+	var messageIDs []string
+	for rows.Next() {
+		var messageID string
+		if err := rows.Scan(&messageID); err != nil {
+			rows.Close()
+			return err
+		}
+		messageIDs = append(messageIDs, messageID)
+	}
+	if err := rows.Err(); err != nil {
+		rows.Close()
+		return err
+	}
+	if err := rows.Close(); err != nil {
+		return err
+	}
+	for _, messageID := range messageIDs {
+		meta, err := a.nextIMAPMetadata(ctx, a.db, folderID)
+		if err != nil {
+			return err
+		}
+		if _, err := a.db.ExecContext(ctx, `UPDATE messages SET imap_uid=?,imap_modseq=? WHERE id=?`, meta.UID, meta.ModSeq, messageID); err != nil {
+			return err
+		}
+	}
+	var maxUID, maxModSeq int64
+	if err := a.db.QueryRowContext(ctx, `SELECT COALESCE(MAX(imap_uid),0),COALESCE(MAX(imap_modseq),1) FROM messages WHERE folder_id=?`, folderID).Scan(&maxUID, &maxModSeq); err != nil {
+		return err
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE folders SET uid_next=MAX(uid_next,?),highest_modseq=MAX(highest_modseq,?) WHERE id=?`, maxUID+1, maxModSeq, folderID)
+	return err
+}
+
+func (a *App) newUIDValidity() int64 {
+	value := a.now().UTC().Unix()
+	if value <= 0 {
+		return time.Now().UTC().Unix()
+	}
+	return value
+}
+
+func (a *App) nextIMAPMetadata(ctx context.Context, db dbExecutor, folderID string) (imapMetadata, error) {
+	if folderID == "" {
+		return imapMetadata{}, nil
+	}
+	rowDB, ok := db.(dbQueryer)
+	if !ok {
+		return imapMetadata{}, nil
+	}
+	var nextUID, highestModSeq int64
+	err := rowDB.QueryRowContext(ctx, `SELECT uid_next,highest_modseq FROM folders WHERE id=?`, folderID).Scan(&nextUID, &highestModSeq)
+	if err != nil {
+		return imapMetadata{}, err
+	}
+	if nextUID < 1 {
+		nextUID = 1
+	}
+	nextModSeq := highestModSeq + 1
+	if nextModSeq < 1 {
+		nextModSeq = 1
+	}
+	if _, err := db.ExecContext(ctx, `UPDATE folders SET uid_next=?,highest_modseq=MAX(highest_modseq,?) WHERE id=?`, nextUID+1, nextModSeq, folderID); err != nil {
+		return imapMetadata{}, err
+	}
+	return imapMetadata{UID: nextUID, ModSeq: nextModSeq}, nil
+}
+
+func (a *App) bumpFolderModSeq(ctx context.Context, folderID string) (int64, error) {
+	return a.bumpFolderModSeqWithDB(ctx, a.db, folderID)
+}
+
+func (a *App) bumpFolderModSeqWithDB(ctx context.Context, db dbExecutor, folderID string) (int64, error) {
+	if folderID == "" {
+		return 0, nil
+	}
+	rowDB, ok := db.(dbQueryer)
+	if !ok {
+		return 0, nil
+	}
+	var current int64
+	if err := rowDB.QueryRowContext(ctx, `SELECT highest_modseq FROM folders WHERE id=?`, folderID).Scan(&current); err != nil {
+		if err == sql.ErrNoRows {
+			return 0, nil
+		}
+		return 0, err
+	}
+	next := current + 1
+	if next < 1 || next == math.MaxInt64 {
+		next = current
+	}
+	if _, err := db.ExecContext(ctx, `UPDATE folders SET highest_modseq=MAX(highest_modseq,?) WHERE id=?`, next, folderID); err != nil {
+		return 0, err
+	}
+	return next, nil
+}
+
+func (a *App) touchMessageIMAPModSeq(ctx context.Context, messageID string) error {
+	var folderID sql.NullString
+	if err := a.db.QueryRowContext(ctx, `SELECT folder_id FROM messages WHERE id=?`, messageID).Scan(&folderID); err != nil {
+		return err
+	}
+	if !folderID.Valid || folderID.String == "" {
+		return nil
+	}
+	modSeq, err := a.bumpFolderModSeq(ctx, folderID.String)
+	if err != nil {
+		return err
+	}
+	if modSeq == 0 {
+		return nil
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE messages SET imap_modseq=? WHERE id=?`, modSeq, messageID)
+	return err
+}
+
+func (a *App) updateMessageModSeq(ctx context.Context, messageID string, folderID string) (int64, error) {
+	if folderID == "" {
+		var dbFolderID sql.NullString
+		if err := a.db.QueryRowContext(ctx, `SELECT folder_id FROM messages WHERE id=?`, messageID).Scan(&dbFolderID); err != nil {
+			return 0, err
+		}
+		if !dbFolderID.Valid || dbFolderID.String == "" {
+			return 0, nil
+		}
+		folderID = dbFolderID.String
+	}
+	modSeq, err := a.bumpFolderModSeq(ctx, folderID)
+	if err != nil {
+		return 0, err
+	}
+	if modSeq == 0 {
+		return 0, nil
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE messages SET imap_modseq=? WHERE id=?`, modSeq, messageID)
+	return modSeq, err
+}

apps/api/internal/app/mail_handlers.go

@@ -84,7 +84,8 @@ func (a *App) handleMailFolders(w http.ResponseWriter, r *http.Request) {
 	}
 	rows, err := a.db.QueryContext(r.Context(), `SELECT f.id,f.name,f.role,
 		COALESCE(SUM(CASE WHEN m.is_read=0 THEN 1 ELSE 0 END),0) AS unread,
-		COUNT(m.id) AS total
+		COUNT(m.id) AS total,
+		f.uid_validity,f.uid_next,f.highest_modseq
 		FROM folders f LEFT JOIN messages m ON m.folder_id=f.id
 		WHERE f.mailbox_id=? GROUP BY f.id,f.name,f.role
 		ORDER BY CASE f.role WHEN 'inbox' THEN 1 WHEN 'sent' THEN 2 WHEN 'drafts' THEN 3 WHEN 'archive' THEN 4 WHEN 'spam' THEN 5 WHEN 'trash' THEN 6 ELSE 99 END, f.name`, mb.ID)
@@ -96,7 +97,7 @@ func (a *App) handleMailFolders(w http.ResponseWriter, r *http.Request) {
 	items := []MailFolder{}
 	for rows.Next() {
 		var f MailFolder
-		if err := rows.Scan(&f.ID, &f.Name, &f.Role, &f.UnreadCount, &f.TotalCount); err != nil {
+		if err := rows.Scan(&f.ID, &f.Name, &f.Role, &f.UnreadCount, &f.TotalCount, &f.UIDValidity, &f.UIDNext, &f.HighestModSeq); err != nil {
 			respondError(w, http.StatusInternalServerError, "failed to scan folders")
 			return
 		}
@@ -154,7 +155,7 @@ func (a *App) respondMailMessageList(w http.ResponseWriter, r *http.Request, whe
 		args = append(args, like, like, like, like, like)
 	}
 	args = append(args, limit+1, offset)
-	query := `SELECT m.id,m.mailbox_id,m.folder_id,COALESCE(f.name,''),m.message_uid,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
+	query := `SELECT m.id,m.mailbox_id,m.folder_id,COALESCE(f.name,''),m.message_uid,m.imap_uid,m.imap_modseq,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
 		FROM messages m LEFT JOIN folders f ON f.id=m.folder_id WHERE ` + where + ` ORDER BY m.received_at DESC LIMIT ? OFFSET ?`
 	rows, err := a.db.QueryContext(r.Context(), query, args...)
 	if err != nil {
@@ -332,7 +333,11 @@ func (a *App) handleMailMessage(w http.ResponseWriter, r *http.Request) {
 		if err := a.updateMessageMaildirFlags(r.Context(), msg.ID, &read, nil); err != nil {
 			a.log.Warn("failed to update maildir read flag", "message_id", msg.ID, "error", err)
 		}
-		_, _ = a.db.ExecContext(r.Context(), `UPDATE messages SET is_read=1, updated_at=? WHERE id=?`, a.now().UTC().Format(time.RFC3339Nano), msg.ID)
+		if modSeq, err := a.updateMessageModSeq(r.Context(), msg.ID, msg.FolderID); err == nil && modSeq > 0 {
+			_, _ = a.db.ExecContext(r.Context(), `UPDATE messages SET is_read=1, imap_modseq=?, updated_at=? WHERE id=?`, modSeq, a.now().UTC().Format(time.RFC3339Nano), msg.ID)
+		} else {
+			_, _ = a.db.ExecContext(r.Context(), `UPDATE messages SET is_read=1, updated_at=? WHERE id=?`, a.now().UTC().Format(time.RFC3339Nano), msg.ID)
+		}
 		msg.IsRead = true
 	}
 	respondJSON(w, http.StatusOK, msg)
@@ -814,8 +819,13 @@ func (a *App) handleSaveDraft(w http.ResponseWriter, r *http.Request) {
 		_ = a.db.QueryRowContext(r.Context(), `SELECT COALESCE(SUM(size_bytes),0) FROM attachments WHERE message_id=?`, draftID).Scan(&attachmentBytes)
 		size += attachmentBytes
 	}
-	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET subject=?,to_addrs=?,cc_addrs=?,bcc_addrs=?,sent_at=?,received_at=?,snippet=?,body_text=?,body_html=?,is_read=1,has_attachments=?,size_bytes=?,updated_at=? WHERE id=?`,
-		subject, jsonEncode(compose.To), jsonEncode(compose.CC), jsonEncode(compose.BCC), now.Format(time.RFC3339Nano), now.Format(time.RFC3339Nano), snippetFrom(compose.Text, compose.HTML), compose.Text, compose.HTML, boolInt(hasAttachments), size, now.Format(time.RFC3339Nano), draftID)
+	modSeq, err := a.updateMessageModSeq(r.Context(), draftID, existing.FolderID)
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "failed to update draft")
+		return
+	}
+	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET subject=?,to_addrs=?,cc_addrs=?,bcc_addrs=?,sent_at=?,received_at=?,snippet=?,body_text=?,body_html=?,is_read=1,has_attachments=?,size_bytes=?,imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END,updated_at=? WHERE id=?`,
+		subject, jsonEncode(compose.To), jsonEncode(compose.CC), jsonEncode(compose.BCC), now.Format(time.RFC3339Nano), now.Format(time.RFC3339Nano), snippetFrom(compose.Text, compose.HTML), compose.Text, compose.HTML, boolInt(hasAttachments), size, modSeq, modSeq, now.Format(time.RFC3339Nano), draftID)
 	if err != nil {
 		respondError(w, http.StatusInternalServerError, "failed to update draft")
 		return
@@ -848,6 +858,7 @@ func (a *App) handleDeleteDraft(w http.ResponseWriter, r *http.Request) {
 		respondError(w, http.StatusInternalServerError, "failed to delete draft")
 		return
 	}
+	_, _ = a.bumpFolderModSeq(r.Context(), msg.FolderID)
 	respondJSON(w, http.StatusOK, map[string]any{"ok": true})
 }
 
@@ -1146,7 +1157,12 @@ func (a *App) handleMarkRead(w http.ResponseWriter, r *http.Request) {
 		respondError(w, http.StatusInternalServerError, "failed to update message")
 		return
 	}
-	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET is_read=?, updated_at=? WHERE id=?`, boolInt(read), a.now().UTC().Format(time.RFC3339Nano), msg.ID)
+	modSeq, err := a.updateMessageModSeq(r.Context(), msg.ID, msg.FolderID)
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "failed to update message")
+		return
+	}
+	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET is_read=?, imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END, updated_at=? WHERE id=?`, boolInt(read), modSeq, modSeq, a.now().UTC().Format(time.RFC3339Nano), msg.ID)
 	if err != nil {
 		respondError(w, http.StatusInternalServerError, "failed to update message")
 		return
@@ -1172,7 +1188,12 @@ func (a *App) handleStar(w http.ResponseWriter, r *http.Request) {
 		respondError(w, http.StatusInternalServerError, "failed to update message")
 		return
 	}
-	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET is_starred=?, updated_at=? WHERE id=?`, boolInt(starred), a.now().UTC().Format(time.RFC3339Nano), msg.ID)
+	modSeq, err := a.updateMessageModSeq(r.Context(), msg.ID, msg.FolderID)
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "failed to update message")
+		return
+	}
+	_, err = a.db.ExecContext(r.Context(), `UPDATE messages SET is_starred=?, imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END, updated_at=? WHERE id=?`, boolInt(starred), modSeq, modSeq, a.now().UTC().Format(time.RFC3339Nano), msg.ID)
 	if err != nil {
 		respondError(w, http.StatusInternalServerError, "failed to update message")
 		return
@@ -1215,6 +1236,9 @@ func (a *App) handleDeleteMessage(w http.ResponseWriter, r *http.Request) {
 		a.deleteMessageMaildirFile(r.Context(), msg.ID)
 		a.deleteMessageFiles(r.Context(), msg.ID)
 		_, err = a.db.ExecContext(r.Context(), `DELETE FROM messages WHERE id=?`, msg.ID)
+		if err == nil {
+			_, _ = a.bumpFolderModSeq(r.Context(), msg.FolderID)
+		}
 	} else {
 		trashID, e := a.ensureFolder(r.Context(), msg.MailboxID, "Trash")
 		if e != nil {
@@ -1348,7 +1372,7 @@ func (a *App) loadMessageForRequest(r *http.Request, id string, includeBody bool
 }
 
 func (a *App) messageByID(ctx context.Context, id string, includeBody bool) (*MailMessage, error) {
-	row := a.db.QueryRowContext(ctx, `SELECT m.id,COALESCE(m.mailbox_id,''),COALESCE(m.recipient_addr,''),COALESCE(m.folder_id,''),COALESCE(f.name,'Unregistered'),m.message_uid,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.body_text,m.body_html,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
+	row := a.db.QueryRowContext(ctx, `SELECT m.id,COALESCE(m.mailbox_id,''),COALESCE(m.recipient_addr,''),COALESCE(m.folder_id,''),COALESCE(f.name,'Unregistered'),m.message_uid,m.imap_uid,m.imap_modseq,m.message_id,m.subject,m.from_addr,COALESCE(m.from_name,''),m.to_addrs,m.cc_addrs,m.bcc_addrs,m.sent_at,m.received_at,m.snippet,m.body_text,m.body_html,m.is_read,m.is_starred,m.has_attachments,m.size_bytes
 		FROM messages m LEFT JOIN folders f ON f.id=m.folder_id WHERE m.id=?`, id)
 	msg, err := scanMessageFull(row, includeBody)
 	if err != nil {
@@ -1398,9 +1422,17 @@ func (a *App) insertMessageWithDB(ctx context.Context, db dbExecutor, msg stored
 	if strings.TrimSpace(msg.FolderID) != "" {
 		folderID = msg.FolderID
 	}
+	imapUID, imapModSeq := int64(0), int64(1)
+	if strings.TrimSpace(msg.FolderID) != "" {
+		meta, err := a.nextIMAPMetadata(ctx, db, msg.FolderID)
+		if err != nil {
+			return "", err
+		}
+		imapUID, imapModSeq = meta.UID, meta.ModSeq
+	}
 	recipientAddr := normalizeEmail(msg.RecipientAddr)
-	_, err := db.ExecContext(ctx, `INSERT INTO messages(id,mailbox_id,folder_id,recipient_addr,message_uid,message_id,subject,from_addr,from_name,to_addrs,cc_addrs,bcc_addrs,sent_at,received_at,snippet,body_text,body_html,is_read,is_starred,has_attachments,size_bytes,raw_path,created_at,updated_at)
-		VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`, id, mailboxID, folderID, recipientAddr, msg.MessageUID, msg.MessageID, msg.Subject, msg.From, msg.FromName, jsonEncode(msg.To), jsonEncode(msg.CC), jsonEncode(msg.BCC), msg.SentAt.Format(time.RFC3339Nano), msg.ReceivedAt.Format(time.RFC3339Nano), msg.Snippet, msg.BodyText, msg.BodyHTML, boolInt(msg.IsRead), boolInt(msg.IsStarred), boolInt(hasAttachments), size, msg.RawPath, now, now)
+	_, err := db.ExecContext(ctx, `INSERT INTO messages(id,mailbox_id,folder_id,recipient_addr,message_uid,message_id,subject,from_addr,from_name,to_addrs,cc_addrs,bcc_addrs,sent_at,received_at,snippet,body_text,body_html,is_read,is_starred,has_attachments,size_bytes,raw_path,imap_uid,imap_modseq,created_at,updated_at)
+		VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)`, id, mailboxID, folderID, recipientAddr, msg.MessageUID, msg.MessageID, msg.Subject, msg.From, msg.FromName, jsonEncode(msg.To), jsonEncode(msg.CC), jsonEncode(msg.BCC), msg.SentAt.Format(time.RFC3339Nano), msg.ReceivedAt.Format(time.RFC3339Nano), msg.Snippet, msg.BodyText, msg.BodyHTML, boolInt(msg.IsRead), boolInt(msg.IsStarred), boolInt(hasAttachments), size, msg.RawPath, imapUID, imapModSeq, now, now)
 	if err != nil {
 		return "", err
 	}
@@ -1610,9 +1642,14 @@ func (a *App) deleteMessageFiles(ctx context.Context, messageID string) {
 }
 
 func (a *App) deleteMessage(ctx context.Context, messageID string) {
+	var folderID sql.NullString
+	_ = a.db.QueryRowContext(ctx, `SELECT folder_id FROM messages WHERE id=?`, messageID).Scan(&folderID)
 	a.deleteMessageMaildirFile(ctx, messageID)
 	a.deleteMessageFiles(ctx, messageID)
 	_, _ = a.db.ExecContext(ctx, `DELETE FROM messages WHERE id=?`, messageID)
+	if folderID.Valid && folderID.String != "" {
+		_, _ = a.bumpFolderModSeq(ctx, folderID.String)
+	}
 }
 
 type messageSummaryScanner interface{ Scan(dest ...any) error }
@@ -1621,7 +1658,7 @@ func scanAdminMessageSummary(row messageSummaryScanner) (MailMessage, error) {
 	var msg MailMessage
 	var toJSON, ccJSON, bccJSON, sent, received string
 	var read, starred, hasAtt int
-	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.MailboxAddress, &msg.OwnerEmail, &msg.RecipientAddr, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &read, &starred, &hasAtt, &msg.SizeBytes)
+	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.MailboxAddress, &msg.OwnerEmail, &msg.RecipientAddr, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.IMAPUID, &msg.IMAPModSeq, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &read, &starred, &hasAtt, &msg.SizeBytes)
 	if err != nil {
 		return msg, err
 	}
@@ -1635,7 +1672,7 @@ func scanMessageSummary(row messageSummaryScanner) (MailMessage, error) {
 	var msg MailMessage
 	var toJSON, ccJSON, bccJSON, sent, received string
 	var read, starred, hasAtt int
-	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &read, &starred, &hasAtt, &msg.SizeBytes)
+	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.IMAPUID, &msg.IMAPModSeq, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &read, &starred, &hasAtt, &msg.SizeBytes)
 	if err != nil {
 		return msg, err
 	}
@@ -1650,7 +1687,7 @@ func scanMessageFull(row messageSummaryScanner, includeBody bool) (MailMessage,
 	var toJSON, ccJSON, bccJSON, sent, received string
 	var read, starred, hasAtt int
 	var bodyText, bodyHTML string
-	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.RecipientAddr, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &bodyText, &bodyHTML, &read, &starred, &hasAtt, &msg.SizeBytes)
+	err := row.Scan(&msg.ID, &msg.MailboxID, &msg.RecipientAddr, &msg.FolderID, &msg.Folder, &msg.MessageUID, &msg.IMAPUID, &msg.IMAPModSeq, &msg.MessageID, &msg.Subject, &msg.From, &msg.FromName, &toJSON, &ccJSON, &bccJSON, &sent, &received, &msg.Snippet, &bodyText, &bodyHTML, &read, &starred, &hasAtt, &msg.SizeBytes)
 	if err != nil {
 		return msg, err
 	}

apps/api/internal/app/maildir_sync.go

@@ -405,13 +405,38 @@ func (a *App) attachMaildirRawPathToExisting(ctx context.Context, mailboxID, fol
 
 func (a *App) syncExistingMaildirMessageState(ctx context.Context, mailboxID, folderID, rawPath, messageID string, read, starred bool) (bool, error) {
 	now := a.now().UTC().Format(time.RFC3339Nano)
-	res, err := a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,is_read=?,is_starred=?,updated_at=? WHERE mailbox_id=? AND raw_path=?`,
-		folderID, rawPath, boolInt(read), boolInt(starred), now, mailboxID, rawPath)
-	if err != nil {
-		return false, err
+	var samePathID, oldFolderID string
+	var oldRead, oldStarred int
+	var oldModSeq int64
+	err := a.db.QueryRowContext(ctx, `SELECT id,COALESCE(folder_id,''),is_read,is_starred,imap_modseq FROM messages WHERE mailbox_id=? AND raw_path=?`, mailboxID, rawPath).Scan(&samePathID, &oldFolderID, &oldRead, &oldStarred, &oldModSeq)
+	if err == nil {
+		if oldFolderID != folderID {
+			if oldFolderID != "" {
+				if _, err := a.bumpFolderModSeq(ctx, oldFolderID); err != nil {
+					return false, err
+				}
+			}
+			meta, err := a.nextIMAPMetadata(ctx, a.db, folderID)
+			if err != nil {
+				return false, err
+			}
+			_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,is_read=?,is_starred=?,imap_uid=?,imap_modseq=?,updated_at=? WHERE id=?`,
+				folderID, rawPath, boolInt(read), boolInt(starred), meta.UID, meta.ModSeq, now, samePathID)
+			return err == nil, err
+		}
+		modSeq := oldModSeq
+		if oldRead != boolInt(read) || oldStarred != boolInt(starred) {
+			modSeq, err = a.bumpFolderModSeq(ctx, folderID)
+			if err != nil {
+				return false, err
+			}
+		}
+		_, err = a.db.ExecContext(ctx, `UPDATE messages SET raw_path=?,is_read=?,is_starred=?,imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END,updated_at=? WHERE id=?`,
+			rawPath, boolInt(read), boolInt(starred), modSeq, modSeq, now, samePathID)
+		return err == nil, err
 	}
-	if rows, _ := res.RowsAffected(); rows > 0 {
-		return true, nil
+	if err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return false, err
 	}
 	if strings.TrimSpace(messageID) == "" {
 		return false, nil
@@ -461,7 +486,20 @@ func (a *App) syncExistingMaildirMessageState(ctx context.Context, mailboxID, fo
 		a.removeDuplicateMaildirMessage(ctx, rawPath, mailboxID, folderID, messageID)
 		return false, nil
 	}
-	_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,is_read=?,is_starred=?,updated_at=? WHERE id=?`, folderID, rawPath, boolInt(read), boolInt(starred), now, chosen.ID)
+	var previousFolderID string
+	if err := a.db.QueryRowContext(ctx, `SELECT COALESCE(folder_id,'') FROM messages WHERE id=?`, chosen.ID).Scan(&previousFolderID); err != nil {
+		return false, err
+	}
+	if previousFolderID != "" && previousFolderID != folderID {
+		if _, err := a.bumpFolderModSeq(ctx, previousFolderID); err != nil {
+			return false, err
+		}
+	}
+	meta, err := a.nextIMAPMetadata(ctx, a.db, folderID)
+	if err != nil {
+		return false, err
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,is_read=?,is_starred=?,imap_uid=?,imap_modseq=?,updated_at=? WHERE id=?`, folderID, rawPath, boolInt(read), boolInt(starred), meta.UID, meta.ModSeq, now, chosen.ID)
 	return err == nil, err
 }
 
@@ -518,9 +556,16 @@ func (a *App) cleanupMissingMaildirMessages(ctx context.Context) (int, error) {
 	}
 	for _, it := range missing {
 		a.deleteMessageFiles(ctx, it.ID)
+		var folderID sql.NullString
+		_ = a.db.QueryRowContext(ctx, `SELECT folder_id FROM messages WHERE id=?`, it.ID).Scan(&folderID)
 		if _, err := a.db.ExecContext(ctx, `DELETE FROM messages WHERE id=?`, it.ID); err != nil {
 			return 0, err
 		}
+		if folderID.Valid && folderID.String != "" {
+			if _, err := a.bumpFolderModSeq(ctx, folderID.String); err != nil {
+				return 0, err
+			}
+		}
 	}
 	return len(missing), nil
 }

apps/api/internal/app/maildir_write.go

@@ -84,7 +84,13 @@ func (a *App) writeRawMessageToMaildirFolder(ctx context.Context, messageID, fol
 		return err
 	}
 	if folderID != "" {
+		oldFolderID := state.FolderID
 		state.FolderID = folderID
+		if updateFolder && oldFolderID != "" && oldFolderID != state.FolderID {
+			if _, err := a.bumpFolderModSeq(ctx, oldFolderID); err != nil {
+				return err
+			}
+		}
 	}
 	if state.MailboxID == "" || state.FolderID == "" {
 		return nil
@@ -132,16 +138,45 @@ func (a *App) writeRawMessageToMaildirFolder(ctx context.Context, messageID, fol
 		a.removeMaildirPath(ctx, state.RawPath)
 	}
 	if updateFolder {
-		_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,updated_at=? WHERE id=?`, state.FolderID, finalPath, a.now().UTC().Format(time.RFC3339Nano), messageID)
+		if state.IMAPUID > 0 && folderID == "" {
+			modSeq, metaErr := a.bumpFolderModSeq(ctx, state.FolderID)
+			if metaErr != nil {
+				return metaErr
+			}
+			_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END,updated_at=? WHERE id=?`, state.FolderID, finalPath, modSeq, modSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
+		} else {
+			meta, metaErr := a.nextIMAPMetadata(ctx, a.db, state.FolderID)
+			if metaErr != nil {
+				return metaErr
+			}
+			_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,imap_uid=?,imap_modseq=?,updated_at=? WHERE id=?`, state.FolderID, finalPath, meta.UID, meta.ModSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
+		}
 	} else {
-		_, err = a.db.ExecContext(ctx, `UPDATE messages SET raw_path=?, updated_at=? WHERE id=?`, finalPath, a.now().UTC().Format(time.RFC3339Nano), messageID)
+		modSeq, metaErr := a.bumpFolderModSeq(ctx, state.FolderID)
+		if metaErr != nil {
+			return metaErr
+		}
+		_, err = a.db.ExecContext(ctx, `UPDATE messages SET raw_path=?,imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END,updated_at=? WHERE id=?`, finalPath, modSeq, modSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
 	}
 	return err
 }
 
 func (a *App) moveMessageMaildir(ctx context.Context, messageID, targetFolderID string) error {
 	if strings.TrimSpace(a.cfg.MaildirRoot) == "" {
-		_, err := a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?, updated_at=? WHERE id=?`, targetFolderID, a.now().UTC().Format(time.RFC3339Nano), messageID)
+		state, stateErr := a.maildirMessageState(ctx, messageID)
+		if stateErr != nil {
+			return stateErr
+		}
+		if state.FolderID != "" && state.FolderID != targetFolderID {
+			if _, err := a.bumpFolderModSeq(ctx, state.FolderID); err != nil {
+				return err
+			}
+		}
+		meta, metaErr := a.nextIMAPMetadata(ctx, a.db, targetFolderID)
+		if metaErr != nil {
+			return metaErr
+		}
+		_, err := a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,imap_uid=?,imap_modseq=?,updated_at=? WHERE id=?`, targetFolderID, meta.UID, meta.ModSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
 		return err
 	}
 	state, err := a.maildirMessageState(ctx, messageID)
@@ -191,7 +226,16 @@ func (a *App) moveMessageMaildir(ctx context.Context, messageID, targetFolderID
 			return err
 		}
 	}
-	_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,updated_at=? WHERE id=?`, targetFolderID, targetPath, a.now().UTC().Format(time.RFC3339Nano), messageID)
+	if state.FolderID != "" && state.FolderID != targetFolderID {
+		if _, err := a.bumpFolderModSeq(ctx, state.FolderID); err != nil {
+			return err
+		}
+	}
+	meta, err := a.nextIMAPMetadata(ctx, a.db, targetFolderID)
+	if err != nil {
+		return err
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE messages SET folder_id=?,raw_path=?,imap_uid=?,imap_modseq=?,updated_at=? WHERE id=?`, targetFolderID, targetPath, meta.UID, meta.ModSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
 	return err
 }
 
@@ -274,7 +318,11 @@ func (a *App) updateMessageMaildirFlags(ctx context.Context, messageID string, r
 	if err := os.Rename(state.RawPath, targetPath); err != nil {
 		return err
 	}
-	_, err = a.db.ExecContext(ctx, `UPDATE messages SET raw_path=?,updated_at=? WHERE id=?`, targetPath, a.now().UTC().Format(time.RFC3339Nano), messageID)
+	modSeq, err := a.bumpFolderModSeq(ctx, state.FolderID)
+	if err != nil {
+		return err
+	}
+	_, err = a.db.ExecContext(ctx, `UPDATE messages SET raw_path=?,imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END,updated_at=? WHERE id=?`, targetPath, modSeq, modSeq, a.now().UTC().Format(time.RFC3339Nano), messageID)
 	return err
 }
 
@@ -336,19 +384,21 @@ func (a *App) backfillSQLiteMessagesToMaildir(ctx context.Context) (int, error)
 }
 
 type maildirMessageState struct {
-	MailboxID string
-	FolderID  string
-	MessageID string
-	RawPath   string
-	IsRead    bool
-	IsStarred bool
+	MailboxID  string
+	FolderID   string
+	MessageID  string
+	RawPath    string
+	IsRead     bool
+	IsStarred  bool
+	IMAPUID    int64
+	IMAPModSeq int64
 }
 
 func (a *App) maildirMessageState(ctx context.Context, id string) (maildirMessageState, error) {
 	var state maildirMessageState
 	var mailboxID, folderID sql.NullString
 	var read, starred int
-	err := a.db.QueryRowContext(ctx, `SELECT mailbox_id,folder_id,message_id,raw_path,is_read,is_starred FROM messages WHERE id=?`, id).Scan(&mailboxID, &folderID, &state.MessageID, &state.RawPath, &read, &starred)
+	err := a.db.QueryRowContext(ctx, `SELECT mailbox_id,folder_id,message_id,raw_path,is_read,is_starred,imap_uid,imap_modseq FROM messages WHERE id=?`, id).Scan(&mailboxID, &folderID, &state.MessageID, &state.RawPath, &read, &starred, &state.IMAPUID, &state.IMAPModSeq)
 	if err != nil {
 		return state, err
 	}

apps/api/internal/app/personal_handlers.go

@@ -1091,7 +1091,11 @@ func (a *App) applyRuleActions(ctx context.Context, mailboxID, messageID string,
 			if err := a.updateMessageMaildirFlags(ctx, messageID, nil, &starred); err != nil {
 				return err
 			}
-			if _, err := a.db.ExecContext(ctx, `UPDATE messages SET is_starred=1, updated_at=? WHERE id=?`, now, messageID); err != nil {
+			modSeq, err := a.updateMessageModSeq(ctx, messageID, "")
+			if err != nil {
+				return err
+			}
+			if _, err := a.db.ExecContext(ctx, `UPDATE messages SET is_starred=1, imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END, updated_at=? WHERE id=?`, modSeq, modSeq, now, messageID); err != nil {
 				return err
 			}
 		case "mark-read":
@@ -1099,7 +1103,11 @@ func (a *App) applyRuleActions(ctx context.Context, mailboxID, messageID string,
 			if err := a.updateMessageMaildirFlags(ctx, messageID, &read, nil); err != nil {
 				return err
 			}
-			if _, err := a.db.ExecContext(ctx, `UPDATE messages SET is_read=1, updated_at=? WHERE id=?`, now, messageID); err != nil {
+			modSeq, err := a.updateMessageModSeq(ctx, messageID, "")
+			if err != nil {
+				return err
+			}
+			if _, err := a.db.ExecContext(ctx, `UPDATE messages SET is_read=1, imap_modseq=CASE WHEN ? > 0 THEN ? ELSE imap_modseq END, updated_at=? WHERE id=?`, modSeq, modSeq, now, messageID); err != nil {
 				return err
 			}
 		case "label":

apps/api/internal/app/types.go

@@ -57,11 +57,14 @@ type Alias struct {
 }
 
 type MailFolder struct {
-	ID          string `json:"id"`
-	Name        string `json:"name"`
-	Role        string `json:"role"`
-	UnreadCount int    `json:"unreadCount"`
-	TotalCount  int    `json:"totalCount"`
+	ID            string `json:"id"`
+	Name          string `json:"name"`
+	Role          string `json:"role"`
+	UnreadCount   int    `json:"unreadCount"`
+	TotalCount    int    `json:"totalCount"`
+	UIDValidity   int64  `json:"uidValidity"`
+	UIDNext       int64  `json:"uidNext"`
+	HighestModSeq int64  `json:"highestModseq"`
 }
 
 type MailLabel struct {
@@ -81,6 +84,8 @@ type MailMessage struct {
 	FolderID       string       `json:"folderId"`
 	Folder         string       `json:"folder"`
 	MessageUID     string       `json:"messageUid"`
+	IMAPUID        int64        `json:"imapUid"`
+	IMAPModSeq     int64        `json:"imapModseq"`
 	MessageID      string       `json:"messageId"`
 	Subject        string       `json:"subject"`
 	From           string       `json:"from"`