Setting up a CNAME record for any one of the domain names or subdomains that you have within a hosting account will permit you to point it to a different domain/subdomain. The forwarded domain address will lose all its records - A, MX and so on, and will take the records of the domain it's being directed to. In this light, you simply can't set up a CNAME record to forward your domain name to a third-party company and retain a working email service with the first provider. It's also very important to know that a CNAME record is always a string of words and not a number because it is generally wrongly identified as the A record of the domain being redirected. One of the main uses of a CNAME record is to point a domain you own through one provider to the servers of another provider assuming you have created an Internet site with the latter. In this way, the website will appear under your own domain, not under some subdomain provided by the third-party provider.