Are PMs really private?

I am currently having problems with a forum based contained by America. They have told me off, won't go into the details here sufficed to right to be heard I can't see what the problem is. The problem I have is that people have private messaged me on their forums and they hold said that I am not allowed to offer them support via PMs regarding the software that the company who host the forums supply. They (the company) have thus been reading my private messages to people. What is the trial stance on this. I am pretty sure that this is a breach of common-law copyright as the PM was never addressed to them and so they should not be able to read them even though they own the forum software? Am I not right on this? By the road I am from the UK and the forum is US based.

Thanks for any help on this.
A US based forum hand will probably rely on US law and on the terms of service that the forum operator have written. Basically, they get to write all the rules and you don't get the right to complain in the region of them.

Private messages are shielded from the view of everyone using the forum. In that sense, they are private. But while you are conducting your correspondence on someone else's servers, you should expect that the owner of the server has full access to those files.

Sorry, but I don't think you enjoy any recourse here.
There is not a simple answer to this question; for one thing, international law differs like wildfire on privacy matters.

In the United States there is the legal concept of a "believable expectation of privacy," but don't get too excited -- many justices differ widely on what this expectation is, or if it even exists.

Add to this the fact that ownership of wires and servers may alter the "ownership" of content (see e.g. DMCA, especially debate in the region of "safe harbor" provisions), and you'll find out that they answer to your question is immensely complex and probably nobody could give you an honest, correct, definitive answer short pursuing it in court.