Hi, I relay transactional mail for my customer's web sites. Each website has it's own SASL authenticated account and mail are sent via submission or smtps.
But, some website doesn't verify email existence when a user submit a web form or 'create an account'. That's why I often see my postfix relay trying to send to non-existing email. Sending again and again to non-existing mail can lowering my IP reputation and waste ressources that's why I need a solution. I can't force my customer to use some kind of email verification but I strongly encouraged them to do it. Most of them don't care or have no time/money/knowlegde to do it. Fisrt, I need to have some stats about outgoing mail. - What percentage of error 'User unknown' per account ? (Can you confirm that every SMTP software bounce with error '550 5.1.1' ?) If someone can advice any script, I will be very grateful. Otherwise, i will write it myself. With these stats, I can then take necessary actions (lock account, …) Second, maybe additional, I think about maintain a list of 'User unknown' address. Maybe, I could implement this (example with plain text file but it could be SQL): # master.cf submission inet n - - - - smtpd -o smtpd_recipient_restrictions=check_recipient_access,hash:/etc/postfix/unknonwn_recipients,permit_sasl_authenticated,permit_mynetworks,reject smtps inet n - - - - smtpd -o smtpd_tls_wrappermode=yes -o smtpd_recipient_restrictions=check_recipient_access,hash:/etc/postfix/unknonwn_recipients,permit_sasl_authenticated,permit_mynetworks,reject $ cat /etc/postfix/unknonwn_recipients bad_us...@example.com REJECT Unknown user bad_us...@example.com REJECT Unknown user And write a cron job to parse postfix logs and add 'Unknown user' email to /etc/postfix/unknonwn_recipients. Thank you for your feedback. Alexandre
