if he knows ur email, he can find out ur email pw, and then simply use the forgot pw, and acclaim/gt sends it on that email
of course that finding the pw of an email its not that easy, and by using the progs that do such things, u risk urself, as those files are infected as well
so unless e made his own program (HIGLY DOUBT IT LOL), he can't be much of a threat, still for safe use, make a 2nd email, and use it only for these kind of stuff (black market, etc) so u lose nothing