Why do PM's just sit in my outbox for days????

Why do PM’s just sit in my outbox for days???

Because the recipient hasn’t read it. When they do it moves to your sent folder.

makes sense…
thanks

in some cases - isn’t it also because people’s inboxes are full?

Could be, if so they would just have to delete old messages so that the new ones can come through (by clicking “release on-hold messages” at top of inbox).