Here's my case: I am the owner of a large forum - a unofficial car owners club.
On my forum, there's particular topic dedicated to car documentation (manuals, user guides, etc.).
In this topic people are posting requests for repair and maintenance (copyrighted) manuals and leave their e-mail address in the post so that others who have it can send it.
Some reply back with "thanks", others with "check your e-mail Inbox".
I received an e-mail from the copyright owner saying that I'm infringing their rights by allowing distribution of their material.
They are also saying that it doesn't matter if it's done in private, it's the same thing.
Now, I know that as a forum owner/administrator it's agains the law to read or disclose the users private messages. So I don't look into them. I don't know what's going on there.
My forum does not allow uploading files, it does not host any copyrighted files/material and also does not allow posting links to file-sharing sites with the respective manuals.
In this topic, I have stated that we do not allow people distributing copyrighted materials via my forum.
My moderators are also doing regular cleaning of the topic, taking down any link like this.
Q1: Am I, as the forum owner, liable in any way?
Q2: If the users are sending links via Private Messaging, and the copyright owner somehow managed to get such a message from another user (this will be his proof), how can I protect myself since it's against the law to look into people's private messages?