The emails and posts probably just share the same database on censored words so that they get [bleeped] no matter what/where/how/when. It might be just the way the software is set up and not worth the trouble to re-write even if someone wanted to make that distinction. Let's not make things seem more intentionally evil than they already seem to some.
Well I have to admit that I was curious about this. So I sent myself an email through this system including some words I know are censored here. All came through in the clear. I would have been surprised had it been otherwise.
Censorsing text that is displayed publicly in a forum is pretty consistent with a design of a message board. After all, there are really some words that are unlikely to be used except in very negative connotations, which most people running a message board would tend to want to filter out from public view if a poster got a bit carried away with their language.
Censoring text sent to someone privately through email is surprising to me, to say the least. Personally, I fail to see where it is any business of the person running the site what sort of language one person may use in a private message to another. But not being one to typically use such words in daily conversation via email, I really can't say if this is normal procedure or not in any other message board system.