Mail Improvements

It'd be nice if we fixed some issues with our mail system and added more features.

Backup Server
If hermes dies, we are screwed. We also don't have any testing machines to test any of these new features on.
 * Make an AFS backup of stuff ( see DRBD, old work on heartbeat/afs)
 * This would require manual intervention to turn to the backup server, because salvaging the volumes takes a long time
 * Set up DRBD for mailman
 * Make sure mailman on both machines is the same version
 * Set up postfix on backup server and test delivery
 * Set up dovecot on backup server and test

Seive
Seive is a replacement for procmail that is secure. We can start using it if we use dovecot-lda to deliver mail. This would replace postfix's "local" as a delivery mechanism.

Dovecot improvements

 * We can move index files to a local partition to speed things up.

Quotas
If we start using dovecot's quota system, we can eliminate the current quota problem where a user can't check their mail. The dovecot quota would be slightly less than the AFS quota, so users would be notified before their quota filled up.

Virtual domains
It would be great if we could host virtual domains. This would require some postfix cleverness and lots of checks. To make it easier, we could require that every final destination be a valid UGCS mailbox (either real user or mailing list). It would also be nice if we could add forwarding aliases without requiring a UGCS mailbox.