what he told me that I didn't turn on so I thought it should be on
When sending private messages the forum can make a copy of the message in your Sent Items folder.
Save a copy of sent messages in my Sent Items folder by default
I got similar problem here. Sometimes, the PM system did not allow me to send some PMs to some users. I did check it out to see my options and options on PM system, it worked finely. But I'll take that, anyway. =/