Backup MX server

["Ross Tsolakidis" <rtsolakidis@powerserve.com.au>]

Hi all,

We have 2 Mail servers, one internal which is our primary and one external which hosts a lot of our clients email.
The external mail server also does some backup MX work for our internal mail server and some of our clients who host their mail at their site.

I want to take the Backup MX domains off our external mail server as its being loaded down heavily when our clients mail servers go down as it puts too much load on it.
Is there a Debian alternative ?
Basically I have a spare box here that I would like to just simply run as a backup MX service.

What apps can I use.
Prefferably something easy to configure..
Enter in the domain that it accepts mail and away you go, etc...

Thanks.

Ross.