Strange problem: I have a distribution group set up on Exchange Server 2010 with around 10 members This group has run fine until I added 2 additional addresses that external clients want to use to email the same distribution group. So now this distribution group is supposed to receive if someone sends to 1 of 3 different email addresses. The e-mail addresses are formatted like this: Blah@Domain.com Blarg@Domain.com Blah.Blarg@Domain.com Internally: All addresses work fine. Myself and others can send to any of the 3 addresses and the distribution group will receive fine Externally: Clients not part of the network cannot send to Blarg@Domain.com Note: Blarg@Domain.com is one of the 2 new ones I added This has also been tested on two personal Gmail and Hotmail accounts. Only 2 of the 3 addresses work even from personal e-mails. The delivery failure notification is received when that specific address is used. Mail flow settings: Accept messages from All Senders Require that all senders are authenticated Not Selected Reject messages from No Senders Default Message size restrictions and Message Moderation Any help will be greatly appreciated One click to automate them all!

What is the exact NDR senders get? Are you doing recipient filtering somewhere? It could be the newly added SMTP addresses havent yet been propagated to the SMTP gateway that does the filtering.

Unfortunately, I have yet to receive the NDR the client gets when sending via outlook. However, I have requested they forward me the error message, so I will post it when I get it. Internally, no NDR is received when using the same address. As far as I can tell, no filtering is being used anywhere. The other addresses assigned to the same distribution group accept messages from the same external personal e-mail accounts that we tested on. Scenario: Sending messages from personal Hotmail account - Send to Blah@Domain.com = Success - Send to Blah.Blarg@Domain.com = Success - Send to Blarg@Domain.com = Fail Failure message from hotmail = This is an automatically generated Delivery Status Notification. Delivery to the following recipients failed. Blarg@Domain.com Would filtering not be based on the distribution group, banning all or none of the 3 addresses associated with that distribution group?One click to automate them all!

Recipient filtering is typically proxyaddress based without consideration of what type of object the address is associated with. Once you get the exact NDR, please post it here.

Good news and bad news. Bad news: The client e-mails are automatically sent by a server to notify the distribution groups of incoming orders and such. So apparently, they had no error messages on their end. They had no idea no messages were getting through, the problem was discovered via a lack of messages on our end. I imagine outlook is not even used in this scenario, so no NDR specific to microsoft. Good news: The client stopped being picky about updating their address books and modified things so the new address that does work is now used. So problem sidestepped...but not really solved. Unfortunate since I was curious about the cause. Ah well. One click to automate them all!

Good news and bad news. Bad news: The client e-mails are automatically sent by a server to notify the distribution groups of incoming orders and such. So apparently, they had no error messages on their end. They had no idea no messages were getting through, the problem was discovered via a lack of messages on our end. I imagine outlook is not even used in this scenario, so no NDR specific to microsoft. Good news: The client stopped being picky about updating their address books and modified things so the new address that does work is now used. So problem sidestepped...but not really solved. Unfortunate since I was curious about the cause. Ah well. One click to automate them all! They could check their SMTP logs if you really wanted to track this down!

You can up the logging for SMTP and test. When doing this, get the partner to send an email to that faule address using Outlook and then ask them to pass the NDR to you to look at. Sukh