I have just set up a new server on a remote site under the same domain as our head office. Users on the remote site (SERVER3) can send e-mails without any problems to users on their site and users at our head office, their mail server is SERVER3.
Users at our head office (SERVER1) can't send e-mails to SERVER3.
The error that is coming back is 'No route found to server SERVER3/DOMAIN from server SERVER1/DOMAIN. Check Server and Connection documents in Name & Address Book.'
The servers are 4.x.