While replying to a fellow hockey players email this evening I ran across a strange mail delivery failed message.

550-x.x.x.x blocked by ldap:ou=rblmx,dc=bellsouth,dc=net
550 Blocked for abuse.  See http://www.att.net/bls_rbl/ for information.

Thought that was rather strange, never been accused of sending spam before and keep a pretty close eye on what’s coming from my machines.

Following the link took me to three resources for third party spam detection databases. They were.
http://www.spamhaus.org/index.lasso
http://www.mail-abuse.com/index.html
http://ipremoval.sms.symantec.com/
When looking up my domain none reported the IP as being on any blacklist but when looking up my routers IP I got some interesting information. This is from mail-abuse.com.

January 20, 2003: If you are a COMCAST customer and are seeing messages that your IP address is on the MAPS DUL, please contact COMCAST directly. You may also want to review this page as well.

If you are a mail user with a standard mail client (such as Eudora, Pegasus Mail, Netscape Mail, or Outlook Express) and you can’t send mail because your IP address appears on the MAPS DUL, it is probably because your mail program is set to use a mail server other than the one your current Internet access provider provides you. Most ISPs usually prevent this type mail relay with their own anti-relay software, but depending on their configuration they may check the MAPS DUL before they check for unauthorized relay.

If you use a mail (SMTP) server on your own computer, or you share your Internet connection with several other people on a local network with a proxy server such as Whistle’s InterJet, and you can’t send mail because of this list, it is because your recipients cannot tell the difference between your legitimate mail delivery and a spammer’s trespassing on their equipment. However, there is a very easy way to work around the MAPS DUL and get your mail through, and it may even speed up your mail in the process.

How about that a message can be seen as spam if the smtp server sending the message is not in the domain of the source IP, i.e. an open mail relay. I guess that would make sense. I may have to start pushing mail through Comcast or switch to imap if this continues.