Separate mail server for each site
We have Head Office and Small Office.
Our mail server is in Head Office - traffic to and from the mail server is over the fast LAN - no problems.
In Small Office, we have two employees, let's call them Snail and Shoe.
Currently Snail and Shoe use the mail server in Head Office. When Snail emails Shoe, the message travels all the way to Head Office saturing the slow link upstream. Shoe then downloads the email from Head Office, which then saturates the slow link downstream.
If Snail and Shoe are on the same LAN in the small office, there shouldn't be any reason for the message to travel all the way back to head office, so my question is:
How do I set up a secondary email server in Small Office using the same email domain in such a way that it would integrate with Head Office?
I envisage a scenario where if Snail sends an email to Shoe, it would go to a local email server in Small Office. The local email server in Small Office would then check if Shoe is located in Small Office or whether he's in Head Office. Seeing that he's in the local Small Office, the local mail server would then keep the message in Small Office. Shoe will then download it from Small Office's local mail server, saving the slow link from saturation.
How do I do set up the servers this way?
Xserve, Mac OS X (10.6.7)