search for: 0badpassword

...e Dovecot auth log line is caused > by a Postfix connection attempt? That would have been my first guess. Why don't you actually try it out (i.e. login in to SMTP with bad credentials) and see if the mysterious log entry appears. # Create bogus SMTP auth string AUTH=`echo "\0user\0badpassword\c" | openssl enc -base64` # SMTP session commands echo "EHLO test.client.helo\nAUTH PLAIN $PW\nQUIT" >data # Use whichever command your Postfix supports "250-AUTH PLAIN" # - if you greet pause, you'll have to enter data manually netcat -C mailserver 25 &l...