On Exchange 2010 some people that reply to one of our emails get an error message of

Delivery has failed to these recipients or groups: 602f5bd2-bcad-4b25-ba5c-7da97b1dd592@prefsol.co.za 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.

But the receiving user gets the email regardless of the error message the sender is receiving. This problem started shortly after we upgraded to exchange 2010.The sender and receiver are in different domains. What is causing the error message and how can I stop it from happening?

For the full error message see the following link http://pastebin.com/WfYbBDBH


That's caused by sending to the "address" (UID) of the old Exchange mailbox. When you did your migration, the mailbox UIDs changed.

There are a couple of possibilities for why this happens.

  1. Client-side issue, probably related to auto-complete.
    • Delete the auto-complete entry (or clear them all) on the senders with this issue
  2. Server-side issue with the mailbox UID addresses.
    • Record the settings and configurations of the mailbox in question, then disable it (remove all Exchange attributes for the AD object)
    • Reattach the mailbox and recreate the required settings and configurations, leaving out any legacy addresses.
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  • Thank you for the reply this helps allot. I just spoke to staff that get this error they say that the it only happens when people reply to their emails, does this not mean that the problem is on the Server-side and not to do with auto-complete on the client-side? – jmtheron Sep 25 '12 at 9:36
  • @Jmtheron Depends. Are these replies to old messages that were first sent before the mail migration? – HopelessN00b Sep 25 '12 at 11:24
  • No the emails were sent after the migration. The 3 people experiencing this problem are the only people in the office that have their email setup on their iPad as well. – jmtheron Sep 25 '12 at 11:50
  • @Jmtheron So, the email that's being replied to was also sent after the migration ended? That seems unlikely. Based on your symptoms, it sounds like the users are replying to an email that was sent from the old Exchange mailbox, which is why they're replying to the old mailbox address. – HopelessN00b Sep 25 '12 at 11:54

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