Dovecot Issues after Upgrade / Attempted Upgrade

I have three different Virtualmin GPL servers sporting the same issue with dovecot. No users seem to be able to authenticate, or access mail. This seemed to start right about the time that 3.88 was released, but that could be coincidence.

One server still states that it’s on 3.87 (with no available updates), the others are on 3.88. One was upgraded from 3.87, the other was actually a fresh install yesterday.

All there give this error in the maillog:

Sep 24 06:27:37 twist dovecot: auth: Fatal: Unknown authentication mechanism ‘HASH(0x3912708)’

Sep 24 06:27:37 twist dovecot: master: Error: service(auth): command startup failed, throttling

I’ve also seen:

Sep 24 06:33:05 fun dovecot: pop3-login: Disconnected: Inactivity (no auth attempts): rip=::1, lip=::1, mpid=0, secured


Sep 24 06:37:02 taco dovecot: pop3-login: Error: Timeout waiting for handshake from auth server. my pid=22674, input bytes=0

Anyone have any similar issues, and/or a direction to point me in for resolution? Dovecot is really not my area.


There’s a bug that occurred during some installations that caused the Dovecot config to not be correct.

If you edit /etc/dovecot/conf.d/10-auth.conf, look for a line that begins with “auth_mechanisms =”, and change that line to look like this:

auth_mechanisms = plain login

And then restart Dovecot with:

/etc/init.d/dovecot restart

Thank you very much. That made my morning. Well, afternoon at this point, but all the same!

That edit did the trick!