My logging config is as follows:

# doveadm log find Debug: /var/log/dovecot-debug.log Info: /var/log/dovecot.log Warning: /var/log/dovecot.log Error: /var/log/dovecot.log Fatal: /var/log/dovecot.log

However, I'm still getting logs in /var/log/messages which I don't want.  I've looked into /etc/rsyslog.conf for clues, but can't find anything that would point to Dovecot logging to /var/log/messages.

Can anyone point me in the right direction here?

https://doc.dovecot.org/settings/core/?highlight=syslog_facility#core_settin...

One option is to assign a local facility like local0 then in syslog tell it not to log local0 to messages

 For example:
 *.info;mail.none;authpriv.none;cron.none;local0.none    /var/log/messages