Email "Undeliverable" When Replying to Messages After Mailbox Migration

After exporting a mailbox from Exchange using a tool like exmerge and importing that mailbox in a new organization, users will receive a NDR when attempting to reply to existing messages in their mailboxes which came from internal senders.

When the mailbox is exported, it keeps the X.500 addresses of original internal senders ("OIS") in the exported messages rather than the associated SMTP addresses. When the user attempts to reply to one of these messages, Exchange tries to locate the OIS based on the the X.500 address and fails.

To work around this issue, create X.500 addresses for the OIS. To do this on a user-by-user basis:

If the OIS already has an account in the new organization, open the user account properties in AD Users and Computers. If the OIS does not have an account, create a Contact for him/her in AD.
Open the properties of the OIS's user account or contact and go to the E-mail Addresses tab.
Click New... to create a new address.
Choose Custom Address and click OK.
In the E-mail address: field enter the OIS's X.500 address. An easy way to locate this address is to open a message from the OIS in an imported mailbox, right-click on the OIS's name and choose Properties. The X.500 address will be shown in the Display field. Optionally, this address can be found in the legacyExchangeDN attribute using a tool like ADSI Edit if you have access to the OIS's domain.
In the E-mail type: field enter X500 (note, no dot).
Click OK in each window to close and save the changes.

The Microsoft Exchange Team blog also references the ADModify tool which should let you bulk-modify many users. We haven't tried this tool, ourselves.

For more information, also see Microsoft Support article 313324.

Author: ASAK
Created: Feb 5 2008 (last modified Feb 6 2008)
Categories: Exchange Server - Outlook
TechByte #160

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