I have a friend that works for a company (actually started it), that recently moved all of their remote users to Microsoft Exchange Services... To the woes of many, it wasn't the best idea. Why is it that companies don't even try to analyze their individual's needs before making monumental decisions?
Exchange is almost "old-hat." The way of the world is moving away from the days of needing to "have VPN access to the network at work," or even "going to work." Yeah Exchange is quite a handy-dandy server for the large enterprises... I know it extends beyond the boundaries of the network at the office. Most companies would now do wise to re-think their methods.
How much are they spending on internal IT departments; what are they gaining from having the kinds of services Exchange has to offer when there are open source standards taking over the world? I remember when (I know, this dates me... just kidding, but the IT industry moves fast) e-mail was the primary method of communication, both within the enterprise, and without. Now it's considered slow, and we're trying to find ways to turn it into something that already exists... It definitely meets needs, but aren't there more free, and capable projects out there that meet our needs?
Certainly it's wise to assume multi-billion dollar businesses have the capitol to invest in anti-spam technologies that far exceed the capabilities of those installed as add-on applications.
Quite often in the quest for efficiency, we sacrifice... well, efficiency.