Mail from a friend not received
Typically this means that your mailbox is full. It treats quest and progress generated mail separately from player mail, as that can be abused to act as a potentially unlimited storage system for items. Delete several of your old player-to-player mail messages and the other mail should be delivered when there is room.
Do you have 10 undeleted mails in your inbox?
NPC mails don’t add to this count so they would still come through.
That’s good to know…I bet the gold sellers filled my stupid inbox. I’ll check it out when I can.