Werk #19428: Fix POP3-based email active checks crashing with AssertionError
| Component | Checks & agents | ||||||
| Title | Fix POP3-based email active checks crashing with AssertionError | ||||||
| Date | Mar 25, 2026 | ||||||
| Level | Trivial Change | ||||||
| Class | Bug Fix | ||||||
| Compatibility | Compatible - no manual interaction needed | ||||||
| Checkmk versions & editions |
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Previously, the active checks Check email delivery (check_mail_loop), Check Email (check_mail), and Check mailboxes (check_mailboxes) crashed with an AssertionError when using POP3 as the fetch protocol:
AssertionError: Expected tuple with two elements, got (b'+OK 2 messages:', [...], 17)
This is a regression introduced in Checkmk 2.4. IMAP connections were not affected.
Technical background
An internal refactoring of the email response parser introduced assumptions about the response format that were incompatible with Python's poplib library. This has been fixed.