It is against the rules, but people still do it - occasionally the moderators will remove such a post, but not often. (Just as being non-anonymous is a bit of a breach.)
What seems to be quite acceptable is to lightly disguise an e-address, e.g. by spelling out d-o-t and a-t, etc.
I orginally went to the trouble of encoding my address with ROT13/ROT47 when exchanging contact details, but this seems to be a step farther than is necessary.
It's mainly to dissuade recruiters and sales people from using addresses for targeted recruitement/marketing. They (Eng-Tips) had quite a problem with this in the earlier days, or so they told me when I enquired.
