they dont get autodeleted. a pm is a just like a thread - but only one person can "own" it at one time. so you reply and it sends the thread back to the other person, then they reply and it sends it back to you. im not sure, but i think IP is addressing this in 6.1, as there have been lots of complaints.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.
