Outlook 365 can't connect via IMAP to MiaB, Error 0x800CCC0E

Note: This is a problem probably caused by Outlook itself. Please read carefully.

As the title says, I can’t connect to my MiaB instance (v57a on Ubuntu 18.04.6 LTS) via IMAP (SSL/TLS on port 993) with Outlook (Version 2210) anymore. It probably started with the September update, worked once after the previous update and is still broken with the latest update.

The connection fails immediately, only causing the following line in the mail.log (IPs and session id replaced):

Nov 10 12:50:58 imap-login: Info: Disconnected (no auth attempts in 0 secs): user=<>, rip=, lip=, TLS handshaking: SSL_accept() syscall failed: Success, session=<abcdef0123456789>

Has anyone had the same problem and found a solution, like a small config modification?

Additional info:
OS is Windows 10 Pro x64 22H2
AV is Bitdefender Internet Security
Thunderbird works with the same settings - I prefer Outlook, though

Outlook is either using an invalid TLS protocol, there is a TLS error or server side your connection is being rejected