Simple Administration, Dedicated Exchange, Full Control over server and data, built-in Spam/Anivirus filters, Antivirus, Active Sync.

Implement Exchange Mail for select users on a domain. Convert as many users to Exchange while others remain on POP/IMAP.

Cheaper alternativwe to MS Exchange. Cross platform support. Builting Email-Archiving and Compliance

Implement Exchange mail to select POP/IMAP users without any modifications on server or DNS.