When you delete an email, it goes into the Trash folder and stays there for 14 days. After that, it goes into the "Recover Deleted Items" feature and will stay for another 30days (supposedly). After that, it drops off into oblivion and cannot be recovered. However, it may stick around longer. The feature seems to have a life of its own. Mine goes back well over two months right now. I don't know of any way to permanently delete something from that folder myself. You just have to wait for it to vanish on its own.