Sorry if this has been posted, but I don't recall seeing it
1) Allow players to view sent mail.
2) Allow players to cancel unanswered sent mail - this is to allow for any typo mistakes that can and probably have already happened to more than just myself.
3) Add an option to send mail from the friends list when clicking their name (i.e. an option similar to sending a player an ingame tell). This would help prevent name typos when sending mail, especially if players are making exchanges for crowns, energy, and/or materials/Crafted items.
GMs are currently unable to cancel or handle in game mail between players, so if you accidently send an attachment to the wrong player, it's gone, and the only hope left is that the mistaken player will send it back. Given the already decent playerbase it's not hard to send mail to the wrong individual by being a single character off.