Question

Exchange administration question

Exchange 2007, SMTP, Active Directory, NDR

I have an Exchange 2007 organization that contains multiple SMTP domains. AD is configured so that each user has multiple e-mail addresses, one from each SMTP domain. Most of the time, all is well. However, sometimes, (more often than I'd like) if an internal user tries to send a message to another internal user using the alternate address, we get an NDR that says the user does not exist. Even more interesting is the hash it generates in the NDR of the recipient it is trying to find. It tries to query a user like so: user.namesecond_domain@first_domain.local. Of course the lookup will fail this way, but where does it get that address, and why does it work most of the time?

The answer as usual in this type of situation is going to be those 3 dreaded letters - DNS.

Check your configuration and dns event logs for more clues. But it is going to be a misconfiguration in there causing it to append the wrong domain to the address.