Re:I'm just asking, seriously..... (Score 1)

Fully agreed - there is no viable single competitor to Exchange. I wrote an article for Redmond magazine on open source alternatives to Exchange last year and came to the conclusion that any sys admin who tried to replace Exchange with open source would be drawn and quartered. The problem isn't just replicating Exchange; it's achieving interoperability with Outlook. The core services in Exchange can be mapped reasonably closely by open source alternatives but there's a layer of obfuscation with MAPI that makes hosting Outlook messaging accounts on anything but Exchange a non-trivial task. Exchange is one of Microsoft's 5 products that generates more than a billion a year (Server, XP, SQL, Office are the other four) and, IMHO, the most vulnerable to open source encroachment. Outlook is one of the most effective products Microsoft has for preventing migration and until there's a seamless way to tie Outlook with an open source backend, it won't catch. BTW, Jamie Zawinksi wrote a brilliant essay called Groupware Bad while worth looking at.