I think my number one pet peeve with email is the subject line... when the subject line has nothing to do with the message or reply below or is missing entirely... I understand sometimes a thread changes over time, but when digging(searching/sorting) through email months/years later, you really appreciate accurate subject lines....
So pretty please, with sugar on top, clean up your subject lines...
no subject is better than an off-base one...
What do you dislike about emails?