IMAP (Exchange Server on premise) suddently stopped working "EXPUNGE failed"

Infos:

  • Used Zammad version: 6.3.1
  • Used Zammad installation type: docker-compose
  • Operating system: Debian
  • Browser + version:

Expected behavior:

  • eMails get fetched via IMAP

Actual behavior:

  • Suddently stopped working, when testing it shows “1 E-Mail(s) wurden in Ihrem Posteingang gefunden. Sie werden alle aus Ihrem Postfach zu Zammad verschoben.” and after that it fails with “EXPUNGE failed”

I already tried to delete all mails in this mailbox, changed the retention policy (found an article about this error with Exchange Online)… I can access the mailbox with any IMAP client and move around mails.

Please find our documentation:
https://admin-docs.zammad.org/en/latest/channels/microsoft365/accounts/account-setup.html#troubleshooting