OK, I've looked for it. Where is it? On the page when you are getting ready to send a PM? Is there a way to automatically save all sent PM's?
This forum is set up nearly identical to another I use for woodworking and I know that it is possible on that site (I think they both use the same software/technology/black magic).
<font color="red"> OK, I've looked for it. Where is it? </font>
Look below the Instant Faces, and right above the Continue button. There are three boxes (see attached screen shot). To my knowledge, there is no way to change the defaults.