You're misunderstanding Scott.  Both outlook and thunderbird, and in
fact just about every email client that exists can filter the messages
as they come in before they are opened, and route them to
predetermined mailboxes/folders whatever the client's storage metaphor
is.

Here is a link to info for thunderbird filtering:
http://opensourcearticles.com/introduction_to_thunderbird_7

and here is one for outlook filtering:
http://www.uh.edu/infotech/php/template.php?nonsvc_id=578

and another:
http://www.ehow.com/how_5378_set-e-mail.html

You'll be MUCH happier once you set this up... if you have trouble
setting it up, throw the list in digest mode until you get filtering
up and running for a simple workaround so you don't have a million
emails in your inbox overwhelming you everyday.

Jim Akiba