Are there any HOWTOs that detail how to create a backup mail server using Redhat Linux? What'd I like to do is build a Redhat Linux 7.3 server and have higher MX recorsd point to it so if say abc.com's main mail server goes down, email to abc.com goes to MX record 15 which points to the Linux server and then queues there until their main server comes back online and the email can be forwarded from the Linux server to the Exchange Server (or whatever server they are running as their main server). I would appreciate any help in this matter.

Thanks,
Jeff

I have something sort of that way

I forward to an outside mail server

by putting mail.mydomain.com as a final destination and mydomain.com as a relay it will capture david@mail.mydomain.com and deliver it locally, it will relay mydomain.com to outside mail server listening on my ip address which forwards it to my isp pop server which I retrieve with fetchmail


the end result is my mail gets there even if my isp or server is down


However I am using postfix as my delivery agent.

Not sure if this is very helpful