Creating a CNAME record for any of the domain addresses or subdomains that you've got in the hosting account allows you to redirect it to a different domain/subdomain. The forwarded domain will lose all of its records - A, MX and so on, and will take the records of the domain name it is being directed to. In this light, you simply can't create a CNAME record to redirect your domain
to a third-party provider and keep a working e-mail service with the first hosting company. It's also very important to know that a CNAME record is always a string of words and never a number as it's often mistaken for the A record of the domain being redirected. One of the primary uses of a CNAME record is to point a domain that you own through one company to the servers of another company in case you have created a website with the latter. By doing this, the Internet site will appear under your own domain address, not under some subdomain provided by the third-party company.