We have an exisiting Distribution List setup in Exchange 2010 and have been requested:
(i) To restrict sending to it from an individual mailbox.
(ii) Set "require that all senders are authenticated" option in the DL
We've had a test user send in a test email from the mailbox set in the Message Delivery Restrictions for the Distribution List, however they get the following error:
"Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept e-mail from certain senders, or another restriction may be preventing delivery."
Looking at the response from the server, there is a user who has CC'd themselves in the test email that was sent out - Would that cause an issue?