diff --git a/internal/imap/scheduler.go b/internal/imap/scheduler.go
index a406303..86ecf65 100644
--- a/internal/imap/scheduler.go
+++ b/internal/imap/scheduler.go
@@ -81,6 +81,12 @@ func (s *Scheduler) SetAuditLogger(a *audit.Logger) {
 // Start launches the background scheduler goroutine.
 // Call Stop to shut it down gracefully.
 func (s *Scheduler) Start() {
+	if n, err := s.store.ClearStaleSyncRunning(context.Background()); err != nil {
+		s.logger.Error("imap scheduler: clear stale sync_running failed", "err", err)
+	} else if n > 0 {
+		s.logger.Warn("imap scheduler: cleared stale sync_running flags left over from a prior crash/kill", "accounts", n)
+	}
+
 	ctx, cancel := context.WithCancel(context.Background())
 	s.cancel = cancel
 
diff --git a/internal/imap/store.go b/internal/imap/store.go
index e0bda4f..9958450 100644
--- a/internal/imap/store.go
+++ b/internal/imap/store.go
@@ -349,6 +349,21 @@ func (s *Store) UpdateSyncInterval(ctx context.Context, id int64, intervalMin in
 	return nil
 }
 
+// ClearStaleSyncRunning resets sync_running=true for every account back to
+// false. Called once at process startup: sync_running is only ever set on
+// this same process, so any row still marked running is a leftover from a
+// prior process that crashed/was killed mid-sync (the defer in
+// runSyncWithRetry never ran) — without this, the scheduler would skip that
+// account forever (checkAccounts skips accounts with SyncRunning=true).
+// Returns the number of accounts reset.
+func (s *Store) ClearStaleSyncRunning(ctx context.Context) (int, error) {
+	tag, err := s.pool.Exec(ctx, `UPDATE imap_accounts SET sync_running = false WHERE sync_running = true`)
+	if err != nil {
+		return 0, fmt.Errorf("imap store: clear stale sync running: %w", err)
+	}
+	return int(tag.RowsAffected()), nil
+}
+
 // SetSyncRunning marks whether a background sync is currently active for an account.
 func (s *Store) SetSyncRunning(ctx context.Context, id int64, running bool) error {
 	_, err := s.pool.Exec(ctx,