Qmail - Email Scanner Add-on

I wanted to know if there are any good email scanners (I found this one http://qmail-scanner.sourceforge.net/). I know there are lots of uses for scanners, but I wanted to see if I could get an automated email service going.

Basically to have a list of newsletter emails in a database table. You send out emails and with qmail scanning all incoming emails it can see if an email comes in (to a particular email, in this case the FROM email on the newsletter email) then it can scan it and check for an error in the Subject / Body of the email. Based on the scan if it meets a search criteria it can remove the email from the database by running a program, shell script, PHP script, etc. This would make it much easier to maintain a valid list of emails. Also, could be use as another option for users to Opt-out instead of just using a web based form they could send an email to removeme@domain.com with the subject as remove.

Example Email Returned by AOL:
From: Mail Delivery Subsystem <MAILER-DAEMON@aol.com>
Subject:Returned mail: User unknown

The original message was received at Wed, 16 Jun 2004 15:04:50 -0400 (EDT)
from unknown.sagonet.net


Your e-mail is being returned to you because there was a problem with its
delivery. The address which was undeliverable is listed in the section
labeled: “----- The following addresses had permanent fatal errors -----”.

The reason your mail is being returned to you is listed in the section
labeled: “----- Transcript of Session Follows -----”.

The line beginning with “<<<” describes the specific reason your e-mail could
not be delivered. The next line contains a second error message which is a
general translation for other e-mail servers.

Please direct further questions regarding this message to your e-mail

–AOL Postmaster

----- The following addresses had permanent fatal errors -----

----- Transcript of session follows -----
… while talking to air-xh04.mail.aol.com.:
>>> RCPT To:<asdf12345@aol.com>
550 <asdf12345@aol.com>… User unknown