Exchange 2010: NDR with strange addresses when sending mail internally

Question

We are working on deploying Exchange 2010. We are new to this so I apologize if I'm missing something obvious.

We have had AD configured for some time now and are now gradually deploying Exchange 2010. We have had users receive the follow NDR:

From: Microsoft Outlook
Sent: Wednesday, April 20, 2011 4:42 PM
To: Jane Doe
Subject: Undeliverable: Quarterlies

 Delivery has failed to these recipients or groups:

 Jane Doe

<mailto:IMCEAEX-_O%3DWORKPAC_OU%3DEXCHANGE%2B20ADMINISTRATIVE%2B20GROUP%2B20%2ABX8FYD1234SPDLT%2B29_CN%3DRECIPIENTS_CN%3Djdoe@workpac.local>
 The e-mail address you entered couldn't be found. Please check the
 recipient's e-mail address and try to resend the message. If the problem
 continues, please contact your helpdesk.

Questions:

1. What exactly are these addresses? The user used auto-complete via Outlook and this is what it resulted in. Some searches lead me to believe it's something from Outlook's cached addres book? But where did it get it from? These are 2 completely new users in a new Exchange 2010 so it's not stale cache.

2. How do we fix this?

Answer 1

quoted from: http://it.usu.edu/htm/faq/faq_q=1360

"The problem is the cached Outlook nicknames are remember the information from the old Active Directory (Blue). Even though a user types in a fully qualified email address like john.smith@usu.edu outlook remembers john.smith@usu.edu used to be mailto:IMCEAEX-_O=UTAH+20STATE+20UNIVERSITY_OU=FIRST+20ADMINISTRATIVE+20GROUP_CN=RECIPIENTS_CN=johsmi@mail.blue.usu.edu. Outlook tries to simply take the old username from the old domain and put that in the new domain. So it tries to send to mailto:IMCEAEX-_O=UTAH+20STATE+20UNIVERSITY_OU=FIRST+20ADMINISTRATIVE+20GROUP_CN=RECIPIENTS_CN=johsmi@aggies.usu.edu

Which makes the email bounce.

To resolve this issue:

We need to clear the Outlook nickname cache.

On XP/2000 the cache file is here:

C:\Documents and Settings\\Application Data\Microsoft\Outlook\.NK2

Close Outlook and delete the .NK2 file to get Outlook to forget previously entered information.

Under Vista it is here:

C:\Users\\AppData\Roaming\Microsoft\Outlook\.NK2

Close Outlook and delete the .NK2 file to get Outlook to forget previously entered information.

Deleting the .NK2 file only deletes the Outlook Cached addresses it does NOT delete the address book."

Hope this helps!

Answer 2

I agree with Mike. The Outlook clients seem to keep the old addresses cached. But instead of deleting all cached addresses from your Outlook clients (internal and external), you may ask your users to:

1. New mail
2. Type in the first characters of the failed address
3. Delete all entries of the failed address via 'DEL', scrolling up/down via the arrow keys
4. Type in the address again or select it from the GAL via the 'to' field
5. Send the mail.

Outlooks email address auto complete uses the address of the last successful delivery.