Redirects
Make Sure

1) "catch-all" Your catch-all redirect must always be your-domain-name@your-domain-name.org.

2) You cannot name your redirects the same as your POP accounts or mailing lists.

THAT USER ID ALREADY TAKEN?

No problem. Just make a redirect. It looks the same, it works the same (almost), and no one will know!
If you choose a user ID "bob" for instance, and its already taken...simply create a "bob2" and make a redirect that redirects anything sent to "bob@your-domain-name.org" to "bob2@your-domain-name.org". Just make sure you configure your email client to receive mail from the "bob2" account not "bob".