Sometimes I receive an email to my admin account stating that the email I sent to an inva...@mydomain.com was not sent.
The message has an attachment and when you open them down eventually you find a spam email that is FROM the invalid_user@mydomain to a vali...@mydomain.com
How is this happening? What do I look at?
From an external account I teleneted in and sent a message from the inva...@mydomain.com to vali...@mydomain.com. And it worked... so I thought it is an open relay.
But when I try any of the websites etc. to check for this none of them can find an open relay on my mail server.
This is a delivery status notification from icarus,
running the Courier mail server, version 0.47.
The original message was received on Thu, 18 Oct 2007 23:46:17 -0600
from localhost (localhost [127.0.0.1])