Emails

Did your email notify the reciever that it was for a particular person and not for general knowledge? If not, then it could be construed to not have been a confidential communication.

If the forum is hosted on a remote system and anywhere in the terms of the usage agreement it states that all messages are subject to review or mmonitoring, then it is perfectly legal.

My advice is to not put anything into email that you are not willing to say directly to another person's face.

There is a good overview of legal ramifications of email here:
http://www.sgalegal.com/guide/internet.html

ifthe person posting the email is ANY of the parties involved with the email, then they can legally post it anywhere they want.
( sender, to, cc, bcc. any person's email addy apprearing in any of these fields cvan legally post it publicly if they choose. )

no-one receiving an email is legally required to honour a private communication notice. ( but I wouldn't want to do business with people that don't )
an important thing to remember about the internet is that is is designed for sharing information, not to keep it locked up and confidential. if you want a communication to be confidential, use snail mail.
online is essentially public access.