Illegal use of email addresses?

[Kit]

I post to an unmoderated, no registration bulletin board. Several of us have discovered that someone else has posted messages using our email addresses. They are not obscene etc but are clearly designed to cause trouble amongst the genuine users; luckily we keep in touch by other means and have been able to establish that the postings are under false identities.
Are email addresses legally protected? Can anybody post anything using any email address they like and get away with it?

[j2buttonsw]

It is pretty easy to post as someone else (eg [email protected]) but much harder to pick up their mail (since Bill Gates' account is probably password protected). I consider email to be as secure a conventional mail (I too could post a letter on behalf of Bill Gates) and my email address is as legally protected as my home address. As an aside, it was demonstrated on this site that people can post under other users IDs (which is my excuse for posting wrong answers).