I have several groups setup for internal use only. They are all set up identically (just different members), and most work without issues, but I have one group that when sent an email doesn't send to all members of the group. That user can send and receive emails normally, it is only the group emails that he doesn't get.
I have removed him from the group and added him. verified the account is active, sent out tests to other members (all received fine). Let me know if I'm missing something obvious, or you need more information. Thank you