The end is near for Exchange 5.5 as Microsoft terminates product support January 1, 2006. For those who haven't already upgraded or switched, the big question is (as always): Microsoft Windows, Linux, Apple OS X or Other? All communities will find more highly regarded solutions for the enterprise than ever before, spanning both Open Source and Commercial worlds: Bynari Insight Server, eGroupWare, exchange4linux, FirstClass, Kerio MailServer, Kolab Server, Lotus Notes & Domino, Novell GroupWise, Open-Xchange, OpenGroupware and Scalix. Late Additions: Merak Email Server Suite, Zimbra Collaboration Suite.