Question : Problem with 'Reply to' after migrating to a new exchange domain

Hello

We've imported our mailboxes from and Exchange 2003 server into an Exchange 2007 SP1 Server in a new forest. The mailboxes were exported to PST files and then imported into Exchange 2007 SP1.

Both domains and Exchange servers will be active with some users in each domain (for example [email protected], and [email protected]). When user1 replies to an email that was sent from user2 and migrated from the old domain it gives the following error.

The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.

it is trying to send the message to user2 in the new domain however user2 remains in the old domain. is there a way to fix this? Do we need to do something different when exporting?

Answer : Problem with 'Reply to' after migrating to a new exchange domain

You are having this problem because Exchange 2003 delivers mail based on the DN instead of the display name or smtp address when it is sent internally.  When you move a user from one org to another, you lose that information as the mailbox gets stamped with a new DN.  To correct this problem, export the exchangeLegacyDN attribute from AD in the legacy environment.  Import this in to the target environment as an X500 address.  (Custom Address given the name X500.)  This should resolve your issue.