Input Latest Windows Insider and Outlook (Android) Updates cause issues with dovecot on IMAP

[Daedalus3]

Server operating system version

Windows 11 Insider

Plesk version and microupdate number

18.0.46

The latest update in the Windows Insider Channel as well as the Outlook Android app causes Outlook to be unable to connect to the dovecot server on port 993. It took me a little while to figure out what was wrong, so this might be helpful for others and maybe as well for the Plesk Team (@IgorG ) at least for a temporary workaround:

Both Windows and the Android App seem to force to provide the credentials via the md5-digest. Thus both apps provide empty values to the server -the login will fail.

Removing "digest-md5" from "auth_mechanisms" in /etc/dovecot/dovecot.conf will solve this issue.

Note: this should only be a temporary workaround, as digest-md5 is more secure than cram-md5 because it prevents chosen plaintext password attacks.

 

[Daedalus3]

Quick addition: Plesk will overwrite the fix every few hours (which actually is a good thing not only due to security reasons). The "fix" will have to be reapplied once the connection to port 993 fails again.