I didn't want this to turn into an "Exchange sux!" thread, with that level of discourse, but you are right in bringing up existing products.<p>The market is huge, and email will never die. I consider calendar integration as the 'next big thing' (that Exchange has had since before the turn of the century). Exchange and Outlook are successful as a product, yes. I don't consider going up against an entrenched Microsoft (and IBM) a viable business plan <i>in this case</i>, but I am willing to be convinced. There IS a market for hosted Exchange servers that some are already meeting, but "Outlook + Web-Outlook + IMAP elsewhere" does not meet my needs as the IMAP protocol for elsewhere is insufficient.