Can we find out if his email is being checked else where??

My boyfriend has a crazy ex-girlfriend... and after his myspace account was deleted (mysteriously) and now somethings i have sent to him on his personal email (a video i made) has been deleted and now we can't even log onto open his account because it says the pword/username was changed!! We were about to change his pword to see if that help but now he can't even so that... so my question is how can I see what computers have accessed his email other then his... educated answers apprictiaed and thank you in advance!!!