This has been going on for as long as I can remember. I'm in 2 Fleets. One on KDF, one on Federation.
When a member of my fleet sends me a mail, it gets repeated over 15 times depending what side it is on, for every mail. Why? Because it sends to each individual character and not to my Global. This seems like an easy fix. I bring it up because as the game grows I keep getting more duplicate mails. This seems like a simple fix which could greatly benefit us for quality of life. We paid for all those extra slots, so hopefully some time gets spent to deal with our concerns. (I'm not the only one irked by this).
and one important thing would be to show who is the message for. i mean, 99% of the players have more then one toon, so especially with auction house mails it can get weird. you check the mails with one toon and you see only "auction lot expired", but not from which toon. so you have to check mails with every toon till you find the right one and pick up the expired item.
so, like an email interface, the mail interface should have: "from", "to", "date" etc.