Jul 3 22:12:17mailserver postfix/smtpd[6195]: fatal: no SASL authentication mechanisms
Jul 3 22:12:18mailserver postfix/master[4881]: warning: process /usr/libexec/postfix/smtpd pid 6195 exit status 1
Jul 3 22:12:18mailserver postfix/master[4881]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling
This only ever happens in my experience when the authentication method is actually Dovecot. Usually the problem........