Hi! We have an Outlook rule setup to forward emails with a specific word or phrase in the subject to a distribution list. However, when the rule triggers, it results in the following undeliverable message. (The rule is enabled on Support account, and is set to forward to Technical Staff (Technical) account.) Delivery has failed to these recipients or distribution lists: Technical Staff Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator. _____ Sent by Microsoft Exchange Server 2007 Diagnostic information for administrators: Generating server: ###### Technical@##### #550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ## Original message headers: Received: from ##### ([#.#.#.#]) by ##### ([#.#.#.#]) with mapi; Thu, 17 Jun 2010 14:43:23 +0100 Content-Type: application/ms-tnef; name="winmail.dat" Content-Transfer-Encoding: binary From: Support <Support@#####> To: Technical Staff <Technical@#####> Why is this happening and how do we resolve it? Also, we do NOT want to turn off the "Require authentication" for the distribution list. This would mean anybody outside our network could send email messages to it, and we absolutely do not wish to do this. Adding a sender address filter wouldn't be of any use also as most spam is sent from the address it's going to anyway so it would always match. Many thanks in advance.

How about turning off the authentication requirement, and then dropping or bouncing any email from outside the Org to that address in a transport rule?[string](0..33|%{[char][int](46+("686552495351636652556262185355647068516270555358646562655775 0645570").substring(($_*2),2))})-replace " "

Hi driskell, You could refer to below link: http://technet.microsoft.com/en-us/library/bb397214(EXCHG.80).aspx Regards! gavin