At 4PM -0400 on 18/10/12 you (Steven Kiehl) wrote:
I'm using dovecot 1.2.9 in a postfix/dovecot setup and I'm having issues with receiving spam where the "from" header contains an address like accounting@mydomain.com. Is there some way I can filter out these emails coming from outside our network with an account associated with our network which doesn't exist? Do I just need to configure some custom process to evaluate these addresses, or is there some way either in dovecot or spamassassin to do this?
You want to do this in Postfix, with either the smtpd_reject_unlisted_sender parameter or the reject_unlisted_sender policy in smtpd_sender_restrictions. You will need to make sure Postfix has access to the list of valid mailboxes at your domain, which it should have already for recipient checking.
Ben