Wondering if I can have some advice on the correct combination of applications to install/configure. Here is what I want to do:

1. Externally hosted mail server, want to maintain this for external mail
2. Want the facility to handle delivery/receipt of internal mail separately
3. Want to use client email software such as Thunderbird in POP3 mode
4. Make use of Groupware (OX), via web client (until more dev is done on TBird)

I have setup OX using the Quick Install Guide Debian4, and am holding off further install/config until I can get a clearer picture on what to do next.

I will definitely need IMAP for groupware - YES ?
Not sure on Fetchmail and/or Postmail
Not sure on the command combinations required to glue to internal/external users.