linux email server, contact manager ...etc

[Rick]

I have a client that is looking to switch from Windows Exchange Server 
Enterprise, to a full blown linux (opensource (freeware)) CRM, Mail, 
Messaging..etc.server. ( They all use outlook )

Anyone, know of a full feature, that would be a replacement, for a midsize 
office, of 200+ people.

They are will to move to ubuntu...if they can find a direct replacement.


Major Thanks-
Richard