I am setting up co-existence between Exchange 2003 and Exchange 2010.
Exchange 2003 is still where are mail comes in and out for the org. I have configured Exchange 2010 to send mail correctly to Exchange 2003 and then out to the internet using a SEND connector that specifies a 2003 box as the remote host.
The issue is that no one on Exchange 2003 can send email over to Exchange 2010. The users on the 2003 server send an email, and then it is stuck in the Queue message with an unreachable destination" with state "ready".
So far i have:
Verified none of the SMTP Virtual Servers for 2003 are pointing to a smart host and all have basic, anon and Integrated Windows Authenticated checked.
I deleted the Routing Group Connector that was installed via the Exchange 2010 install and created a new bidirectional routing group using EMS on the 2010 box. I have verified it is there both ways and can see it under both Admin groups in Exchange. I have performed an IIS reset on the Exchange 2003 boxes as I saw in a different article that closely matched mine.
This message was rejected due to the current administrative policy by the destination server. Please retry at a later time. If that fails, contact your system administrator.
Telnet from the 2003 to the 2010 server works and mail is delivered.
Not sure as to what I could be missing as I have never encountered this issue after a number of 2010 deployments.