Originally Posted by MisterVlad
server:/home# postconf -n | grep mynetworks
mynetworks = 127.0.0.0/8
proxy_read_maps = $local_recipient_maps $mydestination $virtual_alias_maps $virtual_alias_domains $virtual_mailbox_maps $virtual_mailbox_domains $relay_recipient_maps $relay_domains $canonical_maps $sender_canonical_maps $recipient_canonical_maps $relocated_maps $transport_maps $mynetworks $virtual_mailbox_limit_maps
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
OK... now, just curious, but what did that do?
Till wanted to see your mynetworks
setting. 127.0.0.0/8 is ok (it means that only localhost can send without authentication). Lots of people have additional values there which means that also other hosts can send without authentication, making it easy to abuse the server. But this is not the case here.
But it's possible that spammers are abusing web forms (contact forms) hosted on your server. Maybe that's the reason you got that mail.