We have added a new Exchange 2003 SP2 backend server to an existing Exchange organisation. The existing organisation contains only 1 admin and routing group, containing 1 FE and 1 BE server.
I was able to move a mailbox from the old BE server to the new one. I'm able to send mails from the new server to the old one and outside the organisation as well. I'm able to do an smtp telnet session from the old BE to the new one.
BUT I'm not able to receive anything. The connector is still assigned to the old BE server. All mails remain stuck in the queue pointing to the new one. The old BE knows the mailbox resides on the new one, AD replication seems to work perfectly well.
In message tracking, the last stage is "message routed and queued for remote delivery". After a while the message is re-submitted to the smtp gateway and returns in the queue for remote delivery.