I have been playing since the pre-release weekend and the mail system has been quite the roller coaster ride. One day I send mail fine, the next the mail is down, the next I am not recieving mail. Overall when the mail is operating properly are we able to send mail to players who are offline?
Yes. You should be able to send mail to offline players and receive mail while you are offline. If you experience any lost mail (especially containing items), be sure to put in a support request.