I heard back from the client yesterday that the mail to those users was now flowing properly. It appears to have been an issue with the way I formatted the X500 address.My.Settings.Signature = Nothing

I have a client that tried to install Exchange 2003 a couple of years ago and then they just shut the server off and removed it from the domain. When we went to install SBS2011 for them, we had a bunch of problems relating to the remnants of their abandonded 2003 installation. Now, there are some users that are having internal mail bounce with #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ## messages. The address listed is IMCEAEX-_O=COMPANYNAME_OU=First+20Administrative+20Group_cn=Recipients_cn=user@domain.com. Since it has the First Administrative Group in it, it appears to be from the 2003 install. From my testing: Mail works correctly through OWAThis is not an NK2/Outlook Cache issue as I added a test account onto a machine in my office and it does it.I created an X500 address of /O=COMPANYNAME/OU=First Administrative Group/cn=Recipients/cn=user@domain.com and that didn't helpI had Exchange "update" the OAB and then had the Outlook client clear NK2 cache and download the OAB. Still got NDR.I have scoured ADSIEdit looking for that First Administrative Group address and I cannot find it.The legacyExchangeDN value shows the Exchange 2010 address. I assume that is correct since newly created users show this, too. Where in Exchange can I fing this erroneous address and fix it. Any assistance would be greatly appreciated. My.Settings.Signature = Nothing

I just changed the X500 address that I listed in the original post to not end in @domain.com and I didn't get an NDR. I don't have access to the destination mailbox, so I will have to wait until tomorrow to see if it really worked. I will post any additional information that I find.My.Settings.Signature = Nothing

Hi Tim, Any update for your issue? Regards! TechNet Subscriber Support in forum if you have any feedback on our support, please contact tngfb@microsoft.com 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.<o:p></o:p> Gavin TechNet Community Support