i havent been able to find any real reviews on their service either, but 1000MB space / 50GB bandwith for $50/yr on a windows box is obvious overselling. they do have smartermail installed, and are listed as a partner on the smartertools website, which is how i first heard about them.
edited to add:
i wouldnt be opposed to using their service, as they do offer a 30 day moneyback... and if i lost the $5 monthly it wouldnt kill me. I'll wait for some feedback on them before I decide though.
Hmm... seems like not many others know either!! I believe I found them through the Smartertools page too. I normally don't go with Windows platforms but I really am liking what their package offers as well as the email/panel interfaces (I'm really picky about those).