Servers will be coming down on Monday morning for maintenance focusing on the mail system:

We're planning to take the servers offline on Monday morning for maintenance, focusing on the in-game mail system. US servers will be offline beginning at 6:45 AM EDT, and are expected to return by 11:00 AM EDT. Oceanic servers will be offline at 1:45 PM EDT and are expected to return by 4:30 PM EDT.