private mail gateway
I have two ISPconfig 3 servers on Centos 6.4 and Fedora 15 respectively.
I have created a mail gateway using ISPConfig that talks to another ISPConfig install on the Mail Server, i.e. a private mail gateway that talks to a public mail server.
Currently all our locally intended mail on the local machine goes first to the public server rather than being routed directly to the local recipient.
The public server uses mycompany.com as the email domain, locally I have set a dummy domain called mycompany.net. Except for all mail going out it all works like a charm.