There was a bug in SpamAssassin that hit Jan 1st, 2010. All emails were getting marked with the above error in SpamAssassin, and it was adding 3.5 to the spam score, thus getting blocked by most standard spamassassin configs.

To fix this, simply run sa-update from a linux command line.

Here’s an example:
Client has the domain: yourdomain.com
Client has setup test@yourdomain.com to forward to test@aol.com

A spammer sends a message to test@yourdomain.com. The message is received by the client’s server. It is then forwarded to test@aol.com. The client then logs in to aol and they view the message. The message is nothing more than spam and they then click “Mark as Spam” or “Report Spam”.

Now since the last server to receive the message was their own domain, they’re telling AOL that they’re own domain just sent them spam. Eventually this will lead to AOL and other RBL’s blocking their server! The Internet is mature, but not mature enough for it to follow the forwarding path to notice that the client is trying to report the sender as a spammer and not their own server. When this occurs we usually send the client the following:

Important AOL email forwarding issue –
We’ve been contacted by AOL because your account has been reported for spamming. We worked with them to resolve the issue.

To ensure this doesn’t happen again you should not use the Report as Spam button when checking your email through AOL. You’re actually reporting yourself for spamming.

Here’s Why:
You have your email account with us configured to forward to your aol email address. When a spammer sends you an email message it’s received by our server. Then your email account forwards it to AOL from our server. You receive it at AOL and report it as spam. Aol’s system isn’t smart enough to realize that you’re reporting the spammer from a forwarded message. Instead since the message last went through your account on our server prior to being forwarded to AOL they think you’re reporting your own email address on our system as a source of spam.

Please discontinue reporting spam via AOL or we’ll be forced to remove the AOL forwarder on your account to ensure we don’t get in trouble for the spam complaints.