Dovecot can fail if a new version is deployed, but the old version is still running.

In T1931, it was noted it can be a fatal issue blocking mail delivery, but also authentication for SMTP.

In T1931#32134, @dereckson wrote:

Monitoring could be as simple as:`

tail -n100 /var/log/mail... | grep -q "Dovecot version mismatch" && echo "Dovecot versions don't match" 1>&2 && exit 2

In T1931#30803, @dereckson wrote:

We also need a monitoring script to detect those cases:

Oct 7 00:47:06 hervil dovecot[28342]: imap-login: Fatal: Dovecot version mismatch: Master is v2.3.21, imap-login is v2.3.21.1 (if you don't care, set version_ignore=yes)
Oct 7 00:51:02 hervil dovecot[28342]: pop3-login: Fatal: Dovecot version mismatch: Master is v2.3.21, pop3-login is v2.3.21.1 (if you don't care, set version_ignore=yes)

(And to answer the note in the log message, I guess yes we care as if they log that, those should be kept in sync).

We'll see that scenario each time we update Dovecot, and before the restart.

In T1931#32134, @dereckson wrote:

Monitoring could be as simple as:`

tail -n100 /var/log/mail... | grep -q "Dovecot version mismatch" && echo "Dovecot versions don't match" 1>&2 && exit 2