I have an Exchange 2003 server, configured with a .local domain name. There are a number of organizations and domains on this server.
I created a new Exchange 2010 server, on a new external IP. This server's domain is the .com equivalent of the .local domain from the 2003 server.
I deleted some accounts from the 2003 server. I removed the domains from the recipient policies on the 2003 server.
The new server (2010) is working nicely, sends/receives email no problem.
The issue is that users on the OLD server, who try to email users who are now on the NEW server, get NDR's. It seems the 2003 server is "remembering" that these were once locally connected accounts, but now are "external" addresses.
Basically, users on the old server can't email users on the new server, IF they existing on the old server previously. Everything else is fine...