diff --git a/internal/app/worker/wmail/sync_imap.go b/internal/app/worker/wmail/sync_imap.go
index be0c78d5..31ae71af 100644
--- a/internal/app/worker/wmail/sync_imap.go
+++ b/internal/app/worker/wmail/sync_imap.go
@@ -26,12 +26,16 @@ func (w *WMail) Sync(ctx context.Context) *errx.MailError {
 			}
 
 			// FETCH requires a selected mailbox; the select also arms
-			// CONDSTORE for the ChangedSince filtering.
-			if err := w.SmtpImapData.ImapClient.SelectForSync(box.Name); err != nil {
+			// CONDSTORE for the ChangedSince filtering. An empty mailbox is
+			// skipped: 1:* on zero messages is a server error.
+			count, err := w.SmtpImapData.ImapClient.SelectForSync(box.Name)
+			if err != nil {
 				return err
 			}
-			if err := w.SmtpImapData.ImapClient.FetchChanges(ctx, 0); err != nil {
-				return err
+			if count > 0 {
+				if err := w.SmtpImapData.ImapClient.FetchChanges(ctx, 0); err != nil {
+					return err
+				}
 			}
 
 			w.SmtpImapData.Mailboxes = append(w.SmtpImapData.Mailboxes, &box)
@@ -40,11 +44,14 @@ func (w *WMail) Sync(ctx context.Context) *errx.MailError {
 
 		if befBox.HighestModSeq != box.HighestModSeq {
 			w.SmtpImapData.mailbox = box.UIDValidity
-			if err := w.SmtpImapData.ImapClient.SelectForSync(box.Name); err != nil {
+			count, err := w.SmtpImapData.ImapClient.SelectForSync(box.Name)
+			if err != nil {
 				return err
 			}
-			if err := w.SmtpImapData.ImapClient.FetchChanges(ctx, befBox.HighestModSeq); err != nil {
-				return err
+			if count > 0 {
+				if err := w.SmtpImapData.ImapClient.FetchChanges(ctx, befBox.HighestModSeq); err != nil {
+					return err
+				}
 			}
 		}
 
diff --git a/internal/client/smtpimap/imap/client.go b/internal/client/smtpimap/imap/client.go
index 61559ce7..411e4fa0 100644
--- a/internal/client/smtpimap/imap/client.go
+++ b/internal/client/smtpimap/imap/client.go
@@ -178,14 +178,17 @@ func (c *Client) Mailbox(mailbox string, uidvali, opts *imap.SelectOptions) erro
 	return nil
 }
 
-// SelectForSync opens a mailbox read-only with CONDSTORE enabled. FETCH is
-// only valid against a selected mailbox, so the sync loop must call this
-// before FetchChanges; CONDSTORE on the SELECT is what arms ChangedSince.
-func (c *Client) SelectForSync(mailbox string) *errx.MailError {
-	if _, err := c.client.Select(mailbox, &imap.SelectOptions{ReadOnly: true, CondStore: true}).Wait(); err != nil {
-		return c.handleError(err)
+// SelectForSync opens a mailbox read-only with CONDSTORE enabled and returns
+// its message count. FETCH is only valid against a selected mailbox, so the
+// sync loop must call this before FetchChanges; CONDSTORE on the SELECT is
+// what arms ChangedSince. The count lets the caller skip the fetch entirely
+// for an empty mailbox, where a 1:* set is a server error.
+func (c *Client) SelectForSync(mailbox string) (uint32, *errx.MailError) {
+	data, err := c.client.Select(mailbox, &imap.SelectOptions{ReadOnly: true, CondStore: true}).Wait()
+	if err != nil {
+		return 0, c.handleError(err)
 	}
-	return nil
+	return data.NumMessages, nil
 }
 
 func (c *Client) FetchChanges(ctx context.Context, lastModSeq uint64) *errx.MailError {