I have a mixed Exchange 2003 and Exchange 2007 Exchange organization in the middle of a migration to Exchange 2007. We are starting to re-configure inbound SMTP to point to Exchange 2007 first instead of the older Exchange 2003 system. However, all of a sudden, we are getting errors relaying mail to valid SMTP domains. Exchange 2003 has all our accepted SMTP domains in the recipient policy, no problems there, they are marked as authoratative. Exchange 2007 also has the same list of accepted SMTP domains and are set as authoratative. When incoming mail is coming into Exchange 2007, for valid recipients on one of those accepted domains, we get the error "unable to relay for XXX@valuddomain.com.
Is there some trick to configuring the SMTP settings or accepted domains to support a mixed Exchange 2003 and Exchange 2007 mail system? Should the domains not be marked as authoratative in either system? The mail flow works fine for our main SMTP domain, the one set as default in the recipient policy. I don't know whats going on, but we are losing mail when its routed through Exchange 2007.
I even set the incoming mail to go back through another Exchange 2003 server and its being rejected there, unable to relay. I had to go back to the original Exchange 2003 server for the mail to be accepted. This is really strange.
We have SMTP configured to come through 3 incoming SMTP servers. Its accepted on a server running an anti-spam software that acts as an SMTP proxy. Mail is then delivered to an Exchange 2003 server which then acceptes and routes the mail. Exchange 2007 was installed into our native mode Exchange 2003 organization.
Any ideas?
Thanks
