Re: A study?
I agree, but we do use them.
We had our own, in house, non-exchange email system that was good at spotting a lot of problems ... but it was over cautious. we blocked pretty much all mime-types that might contain infections, we used checksum remote servers, virus checkers, keyword lookup ... everything that we possibly could ...
then we were bought out, and the new company wanted to use Outlook, no choice in the matter this was coming from the new directors, and not for any technical reason.
We moved to Office 365, which has sh*t detection, no email recovery options and everything that is rejected is basically "black box", you have no idea why it was rejected.
thank god(s) that we had the possibility of Mimecast, it pretty much puts back all the stuff I had in my home-grown system, with the addition of sandboxing (which I think is an awesome addition) ...
yeah it costs, yeah the old version was essentially free, but when you're going after a sh*t product to do email, for no sensible technical reason, and you're willing to pay an arm and a leg for it, you may as well pay these guys to do what they do well.