We use several different email servers. I guess the question would be, why does your Prez want to move off of SmarterMail?? What is his reason and what is he trying to attain? From there.. other alternatives could be examined. But as with the post from H. Timmes.. the cost for other platforms could be much more.. and still not obtain the objective of your Prez.
Reason I am rambling is: We have 3 type of email severs running... they all have their plus / minuses... It depends on what you were looking for.