I'm currently researching best possible solution for on premisses Exchange 2013 mail security. I ran across this http://vamsoft.com/
and tested it. While it's very cost effective solution, its is not as dynamic as I need it. You can tight some of the policies to make is very secure but you will start getting a lot false positives to the point when it will start driving user complains. On the other hand if relax it, you may run into getting user mailboxes infected.
I would like to have your opinion what solution will be ideal for 150-200 mailbox setup. Some of the features I would like to see is user managed quarantine policies.