"How can I create a thread, send a PM to a user, or join the chat?
The permissions to create a thread, send and receive PMs, and use the chatroom will be granted automatically after you post a certain secret number of times and are active for at least 24 hours. This is to avoid spam and abuse of accounts.
How do I send a PM after I have permission?
Once you have permission to do so, you can send a PM by going to the information tab of a member's profile. If it gives you an error for spam-like content, check your message, our system identifies it as spam."
^From Rules and FAQ thread :)