Parsing Emails Problem

[Anon]

I'm trying to parse emails sent to a collection box by usernames in which the messsage was sent to.

For example, a msg was sent to [e-mail] and bob userid was unknown to the server, it is rerouted to a collection box, [e-mail].

My script will go through [e-mail] and find all msgs addressed to bob and move it else where.

Now my problem is when there is mailing lists involved. I cannot parse emails in which the headers doesn't show who it is adressed to. The headers below is copied from a msg sent from a mailing list that arrives in my account. How was the email able to determine what user on the domain to address to?

Date: Thu, 15 Jul 1999 21:40:59
Subject: Add Me! Newsletter #46 - Creating A Buzz
To: "Add Me! Newsletter" <[e-mail]>
From: [e-mail]
List-Unsubscribe: <mailto:[e-mail]>
Reply-To: "Add Me! Newsletter" <[e-mail]>

[Anon]

Another thing I was thinking was a way to pipe incoming msgs from a domain directly to a script. This is another way I'm loooking into, but I cannot figure out what I'm suppose to be researching on about sendmail. I'm clueless, so any help is great in this area too.