Microsoft will probably not make a recommendation; they don't have an antivirus product that can be installed on Windows Home Server and aren't in the habit of recommending competitors' products.
As for the general question, search is your friend; a search on
antivirus recommendations will return a very manageable number of hits, among which you should be able to find an answer. Note that if you find mostly old posts, with no new information, that probably should tell you something, perhaps that the old posts
are still relevant...
I'm not on the WHS team, I just post a lot. :)