all sounds interesting
the exchange solution sounds excellent, the only big caveat is not to get any of my outbound email tagged as spam. We've had this in the past and we either lose the booking (say 2 nights = £120ish) as the person doesn't look in theiir junk folder for my email reply, or we decline a booking since we're full etc and people arrive anyway, thinking they have a firm booking! So email really is the lifeblood of our B&B.
Also important to have some decent spam filters on the inbound email that would now be handled by exchange. I get probably 100 spam emails a day but only see 2 or 3 of them, the rest get filtered successfully. And only a few times a year does a proper email get tagged as spam, so that's important too.
Just checked, and we have just one "username" that sends/receives email that is important, one that sends/receives that isn't important so ideally would stay on pop3, and about 6 aliases that received email that feed into the main username.
G