Can Field and Form rules run off of Incidents that are mailed in? 

We're trying to set it up so incidents that are emailed in with a certain subject and sender are sent to the proper group with the correct category set. But the variations of field rules I've tried don't seem to do anything at all on incidents that are emailed in. That's why I'd like to know if they can even run on emailed in request or if they can only run on request made while in ServiceDesk.