We had a user that had been added to a DL under Message Delivery Restrictions > Accept messages from. He had been given the access to delivery to the "All Company" DL. This user had left the company. His mailbox had been removed from his account and the account disabled. The next time I tried to add another user to the "Accept messages from" it threw an error that it couldnt find the other user that is no longer with the company. The user that was terminated was not listed in the GUI as being allowed to send to the DL even though he was actually still in the list. To quickly resolve the issue, I gave him a mailbox and enabled his account. I was then able to see him in the list and remove him. I could then add users to the list. Given more time I am sure I could have removed him from the list via powershell using set-distributiongroup or something similar. I know someone will say just make sure you remove the user from all of the ""Accept messages from" lists but thats not really the answer to this issue as it is it not easy to determine what lists the user is in. I think the real issue is: Should the user be hidden from the GUI if he no longer has a mailbox? ...which causes an error each time another user is added...
What's your opinion?