Setting up a CNAME record for any of the domain addresses or subdomains that you've got in the hosting account allows you to point it to a different domain/subdomain. The forwarded domain name will lose all of its records - A, MX and so forth, and will take the records of the domain name it is being redirected to. In this light, you simply can't create a CNAME record to direct your domain to a third-party company and retain a functional email service with the first hosting company. It is also essential to know that a CNAME record is always a string of words and not a number as it's frequently mistaken for the A record of the domain address being redirected. One of the primary uses of a CNAME record is to direct a domain which you own through one company to the servers of another provider in case you have set up a site with the latter. By doing this, the website will appear under your own domain name, not under some subdomain provided by the third-party company.