Do you have new mail or notifications? If you don't, when you do get mail do a number pip up beside it?
On consoles at least up until pre patch the mail is in menu social (usually an indicator is there) as well as notifications.
That's my guess too but there is no way to interact with what shows on the screen.
No new mail but I did have 2 guild message of the day changes but the on screen shown above do not have any numerical references.
In the game menu as always there are numerical references
-PC (PTS)/Xbox One: NewBlacksmurf
~<{[50]}>~ looks better than *501