Not even close (I'd wish, I used to be a zealot and STILL run Linux, working for a Microsoft based shop). That's only talking client and even there it falls sh

Not even close (I'd wish, I used to be a zealot and STILL run Linux, working for a Microsoft based shop). That's only talking client and even there it falls short. Ignoring that users are happy with one thing for everything mail/contacts/calendar/tasks: What's the editor like in TB (I know, playing devil's advocate)? Auto correction? Can you easily embed weird content and expect it to work on the other side (drag stuff from Excel..)? It sucks, but that's what happens day in and day out. And you ignore the server side. AD is really not that bad. Better than most 'virtual users on postfix' setups, if you go beyond a family or tiny team. Now you need the other server features. Calendar (w/ sharing, rights management -> AD?). Decent sync and push (IMAP IDLE is the closest you might get, I guess) for mobile clients. Delegation (i.e. 'You can write in my name') and out of office replies that don't require Joe User to write sieve scripts. I run my own setup and I am NO fan of Outlook/Exchange, but trying to replace what they do with a random selection of OSS tools will probably fail (and hence they couldn't do it in Munich).