This article is for cPanel Accounts. Determine where your account is with this guide.
You can set up custom MX Records in your cPanel by logging in and selecting the MX Entry button from the Mail menu.
In the "Email Routing" box you will need to select "Remote Mail Exchanger" and click "Change."
Then add an MX Record for the primary email server in the Destination text box. You may need to remove or edit the existing MX to overwrite it. An example for the primary Google Apps mail server [in most instances] is the fully qualified domain name "aspmx.l.google.com" which would be typed into the "Destination" box.
Set the priority for the MX record next, and keep in mind that LOWER priority numbers have a HIGHER priority in the record index. So if you just have one remote mail server to configure the priority needs to be 0 unless otherwise specified by your mail server provider.
Click on the "Add New Record" button when you have all the correct information entered. To add records for additional servers, repeat the above steps for each address. Give your backup MX servers a lower priority than the primary to ensure that e-mail for that domain works as needed.
As mentioned above you may need to remove any existing MX records, or lower their priority to ensure proper e-mail record setup. There will be a "Delete" and "Edit" next to each record for you to take care of them as needed.