I really have a hard time with people saying that Office-Exchange is a killer app...
Now that everyone wants a copy of their email on every possible device they own, I find it a million times easier to have the mail hosted somewhere using Google Apps or outlook.com or any other mail service you prefer. For around 50$/user/year, small and medium-sized companies have absolutely no reason to buy and maintain expensive servers just for Exchange. Support technicians that specialize in Exchange are usually hard to find and/or very expensive, it also requires massive backup infrastructure on antiquated tapes and in case of a crash, restoring is simply painful. Simply not something that I would recommend unless they have full time IT employees (even then).
Then you need static IPs, have to check constantly to make sure you are not on someone spam black list and usually need an ultra-fast connection too for all the people that are on the road to receive and send mail at reasonable speed. Then that still won't protect you if you've got some sort of power failure or internet failure at the office and then nobody is able to receive/send emails until that's solved.
Maybe it still makes some sense for very large organization with full time IT employees but for everybody else, there's the cloud.