Some years ago a purchasing agent (who later disappeared without notice) decided the company should be "all Microsoft" and got a buy-in from the president.
Today, they are not so sold on Microsoft, but they just paid a whole lot of money for Exchange 2003 and Windows 2003 server and the AD conversion (no, they didn't pay it to me - they were trying out a new consultant), so they are psychologically committed to using it.
Given the circumstances, my best course is to keep my mouth shut and take their money. There won't be a real opportunity for change here for a few years now.