Exchange setup created many nuisance domain accounts

New at this, so may be asking the wrong questions. Please advise accordingly.

I've just finished installing Exchange 2013 into my small Server Essentials 2012 R2 domain (I put it on a separate VM from the DC). I worked on it all day yesterday.

Much to my chagrin, I received a Health Report warning this morning that I'd exceeded my 25-account allotment in WSE. Needless to say, this surprised me—I'd only created 10 so far. There should've been plenty of room.

Well, it seems that Exchange Setup had gone and added its own—18 of them, to be exact. Here's what I've got:

Do I really need all of these? What are they used for? How quickly would Exchange go belly-up if I just deleted them all?

I have to do something... I don't know whether the DC's going to shut me down over this, but I'd hate to consider it.