I don't think it's officially possible, but I wonder if you created a request type that auto-assigns to a specific tech and created an action rule that said "If subject contains x, then make request type y"
We implemented this for awhile using action rules. It works but you have to add an action rule for each tech you want to assign to.
Set up an action rule criteria to match ( contains ) on the request text ( not request type ), such as "admin=bob". Setup the action to do what you want, i.e. assign the ticket to bob.
Obviously in the body of your email, add the criteria text that you are matching on. "DRIVE SPACE ALERT yadda yadda .... admin=bob"