A new installlation with 2 email accounts. The second account works fine, but the first throws up a periodical error: “[IMAP] Cannot open folder “/mailboxlist”. (NO [SERVERBUG] Internal error occurred. Refer to server log for more information. [2022-09-22 17:47:16] (0.001 + 0.000 secs).)”
Despite that, emails arrive and can be sent, and test messages are sent and received ok.