MX entry (cPanel)
You can use the MX Entry maintenance function in cPanel to change where a domain's email is delivered to. This allows you to have the email from one domain delivered to another domain, by changing the DNS MX entry for the domain.
You can use this function to create a backup mail exchanger which will receive mail when the primary exchanger goes down. Once the primary exchanger is back up, mail delivery will resume. To do this, you'll need to add a secondary MX entry for your domain with a lower priority than the primary MX entry. Please be aware the 0 is the highest priority and 10 is the lowest.
- http://www.sandh.com/support/mx.htm - What are MX entries?