API Documentation for Privatemsg, Userpoints, User_Relationships and Properties.
This is the (currently inofficial) API documentation of the privatemsg 6.x API.
The site has been updated to Drupal 7 now that API module is available for it. Thanks @jhodgdon for your awesome work on that module!
If you like these modules and how I'm trying to maintained them, you're welcome to make a donation.