# view all queued up mail sudo postqueue -p # delete all queued up mail sudo postsuper -d ALL # add this to /etc/postfix/main.cf smtpd_sender_restrictions = reject_unknown_sender_domain smtpd_helo_restrictions = reject_unknown_helo_hostname # optionally, run this so that it doesn't complain about old files sudo postmap /etc/postfix/virtual # restart mail sudo /etc/init.d/postfix restart # watch log sudo tail -f /var/log/mail.log