If all he mentions are gfe or pse, cuddlng, kissing, you know things that are considered vague or legal, that's fine. If his email flat out says, "Lookie here girl, I want to suck on them tits for 3 hours then double click your mouse until it falls off...." you get the point, I would not be responding period.
If he leads me to another site where his preferences are already listed or if he has a memo in the sig. line like a few others, that is perfectly ok. I just think it's best to keep it out of the emails.