This is a scenario which happens from time to time where you may host your website on a 3rd party server such as Amazon AWS or Microsoft Azure but would like to continue using our services for managing your hosting, email and so on.
In this case the best option is to first go to cPanel then Zone Editor and edit the existing main A record which would have the name "domain.extension." and change the name to something you like such as "mailserver.domain.extension."
Then proceed to creating a new A record. The name should be "domain.extension.", type set to A and the Record should be the IP address of the server hosting your website.
Finally edit the MX record which has the name "domain.extension." and change the destination to the name you set in step one, eg. "mailserver.domain.extension" and also update the record for the cname "mail.domain.extension" to "mailserver.domain.extension"
