My Exchange 2007 Pickup Directory works just fine for internal and external addresses but will not send to distribution lists. The message bounces with the following error: #550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ## Who needs authentication? The client is not connected at this point since I'm using the Pickup Directory. Is the message referring to the polling service? Thanks, Matthew Matthew

check this 1st Go in the properties of the group in the EMC and look under Mail Flow Settings>Message Delivery Restrictions. There is a checkbox "Require that all senders are authenticated". Uncheck it.Sukh

Hi Matthew, You can also try this solution: Remove the adpermission "ms-exch-smtp-accept-authoritative-domain-sender" from the NT Authority\Authenticated Users group by running the following cmdlet: remove-adpermission "connectorname" -user "Nt Authority\Authenticated Users" -extendedrights: ms-exch-smtp-accept-authoritative-domain-sender Any feedback is welcomed.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Sukh, Thank you for the reply, I tried unchecking authentication and it did work. I am also going to try Jidan's recommendation to see if there is a option for all Distribution Lists. MatthewMatthew