I'm looking into a problem for a friend. They run a local Exchange 2010 environment, with one server with the Edge/Hub/Mailbox/CAS roles. They have approximately 20 mailboxes, and 99.9% of the time everything works correctly. The problem is that the odd message, sent between internal exchange users sometimes causes an NDR to be generated and the message is not received. Even more peculiar about this, is that the NDR has absolutely no useful error information. There are no event log errors either. Any suggestions on the next troubleshooting step would be much appreciated. Here's a copy of one of the NDR's: Delivery has failed to these recipients or groups: James Shoemaker A problem occurred during the delivery of this message. Please try to resend the message later. Diagnostic information for administrators: Generating server: /O=TKY EXCHANGE/OU=EXCHANGE ADMINISTRATIVE GROUP (DYDUBVJU72KJUBN)/CN=RECIPIENTS/CN=James Shoemaker6bc16y01 # #TKYEX#

Go into James Shoemaker's mailbox, get-mailbox jshowmaker|fl emailaddresses,legacyexchangedn Do you see him having the address anywhere? /O=TKY EXCHANGE/OU=EXCHANGE ADMINISTRATIVE GROUP (DYDUBVJU72KJUBN)/CN=RECIPIENTS/CN=James Shoemaker6bc16y01 If not then the user that's sending has a bad Outlook nickname cache (pre outlook 2010) or stream_autocomplete.dat in Outlook 2010. Have the user's clear the cache or add the address /O=TKY EXCHANGE/OU=EXCHANGE ADMINISTRATIVE GROUP (DYDUBVJU72KJUBN)/CN=RECIPIENTS/CN=James Shoemaker6bc16y01 as an email address of type x500 in the email address tab of their mailbox.James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

Its looking ExchangeDN value is missing in james user mailbox, Is it migrated mailbox from lrgacy exchange. As james said above, Check whther user mailbox have LegacyExchnageDN value in mailbox. To add LegacyExchnageDN value you can see below article: http://www.simple-talk.com/content/print.aspx?article=628Anil MCC 2011,ITIL V3,MCSA 2003,MCTS 2010, My Blog : http://messagingschool.wordpress.com