I have a 2 server Exchange 2003 environment- 1 BackEnd server and 1 Front End server that has an SMTP connector to route Internet mail in and out to Postini.I added 1 2007 Exchange server running CAS, Hub and Mailbox. The default routing group to connect the 2 systems is set up between the 2007 box and teh BackEnd 2003 server.Everything in this transition state is working except Inbound Internet mail specifically to the new 2007 server. When I try to send in to a mailbox on the 2007 I get an NDR 5.35 a looping condition was detected - the server is configured to route mail back to itself. Not sure how to resolve this?

Think I solved it by deleting the routing group from the 2003 server to the 2007 server and re-adding it specifying both the 2003 servers as allowed to use the connection.