I migrated an organization from Windows2000 SBS w/exchange2000, to Windows2003 Standard Server w/Exchange2003.
There is no real migration path so I ended up creating all the user accounts and mailboxes in the new organization then used Exmerge to export the old mailboxes from the old system, and then used Exmerge to import them back to the new mailboxes.
I changed the MX record to the new server IP address and everything looks good. OUWA works fine, Outlook clients internally connect and have no problem. All is well.
Except, when a user tries to reply to one of the old mails that were migrated we get the following.
Your message did not reach some or all of the intended recipients.
Subject: RE: AC Adapter for Compaq Laptop
Sent: 10/26/2004 8:31 AM
The following recipient(s) could not be reached:
username on 10/26/2004 8:32 AM
The message could not be delivered because the recipient's destination email system is unknown or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email system of the recipient.
Have any ideas as to where to look for this issue? The old domain name and new domain name are the same. Only the resolved IP address changed.