iOS 18 and IMAP, my findings but no solution

We use dovecot as IMAP server. The tests has been done on units that run iOS 18.1 or 18.1.1.

We had a few accounts that stopped working after upgrade while others had no problem. The accounts that still worked had no special characters in their password, only A-Z, a-z, 0-9.

I tried on one of the accounts that didn't work to change the password to the same basic ASCII format but that didn't help even after restart of both the mail server and the iPad. After deleting the mail account and doing a new setup on the iPad the error message that it couldn't connect to the server disappeared but it still didn't download any messages.

My temporary solution for the moment is to install Outlook on the units with problems that works.