I changed a domain from company.org to company.local on a new clean SBS 2003 install this weekend. I found that we have to go in and manually edit the "shared" contacts (after importing into new server) that contained staff email addresses as they were all still trying to go to the old domain and failing. This was an easy fix by just querying the users name against the global address and then saved the corrected contact entry. Problem is now users are replying to old internal email and the replies are failing: " 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." The confusing part of it is that the clients mail domain is still company.org - I just changed the internal domain name to company.local... In AD users email addresses are showing as company.local and company.org. Advice anyone? Can anyone explain what Outlook is using as the source of the senders address when replying to these old emails based on the old global address book? It seems like it's using something other than just the senders smtp address like maybe the ldap properties.. Thanks, TJ