Follow the steps below to troubleshoot issues with email folders not syncing in Outlook for Exchange:

1. Check the server connection by signing out and signing in again.
2. Check the user mailbox size constraints.
3. Verify whether the Outlook version is compatible with the Exchange server.
4. Check synchronization between the user mailbox, folders, appointments, and contacts.
5. Verify whether the data files have been removed from the Exchange server.
6. Check the installed third-party applications for compatibility with Outlook.
7. Check the account settings for various notifications.
8. Verify Outlook’s online mode.
9. Check the IMAP and SMTP configuration.