you get a server error if you accept the mail twice. This is easily done if you hit the mail icon when first loading the game to the ready area (or whatever it is called). Since it also opens the mail screen two copies are opened. You can accept & delete then close the mail screen. With the second mail screen you can accept & delete the mail again. This causes a server error with the mail even though there really was no error other than you trying to accept the same mail twice.

Since you don't have any other information up there, I thought I would just post that information.