Creating a CNAME record for any one of the domain addresses or subdomains you've got in the hosting account allows you to forward it to a different domain/subdomain. The forwarded domain name will lose all of its records - A, MX etc, and will take the records of the domain it is being directed to. In this light, you can't create a CNAME record to forward your domain name to a third-party provider and maintain a working email service with the first provider. Additionally, it is essential to know that a CNAME record is always a string of words and not a number as it's generally mistaken for the A record of the domain being forwarded. One of the main uses of a CNAME record is to direct a domain that you own through one provider to the servers of another company assuming you have set up a website with the latter. In this way, the site will appear under your own domain name, not under some subdomain provided by the third-party company.