Email terrorist
Somebody who bombards your email inbox with (mostly) unnecessary messages. They are most common at work, since you are unlikely to remain friends with such a person in a social capacity. The volume of emails is such that it detracts focus from the key tasks you are looking to undertake whilst on your PC.
Dan: Jees, where's my report already?
Dave: I'm trying, man, but I can't focus. It's Sarah Braun, she's such an email terrorist.