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?
And I did a test via that url, and it came back with 15 tests, all failed, meaning I don't have an open relay.
The reason I posted that, was because my client got that email sent to him, and asked me what it was, and I told him that I don't know... but I will find out