Setting up a CNAME record for any of the domain names or subdomains you have in a hosting account allows you to forward it to a different domain/subdomain. The forwarded domain address will lose all its records - A, MX etc, and will take the records of the domain address it's being redirected to. In this light, you simply can't set up a CNAME record to forward your domain to a third-party company and keep a functional email service with the first hosting company. It's also important to note that a CNAME record is always a string of words rather than a number as it's regularly confused with the A record of the Internet domain being forwarded. One of the main uses of a CNAME record is to forward a domain address that you own through one company to the servers of some other company if you have created an Internet site with the latter. By doing this, the site will appear under your own domain name, not under some subdomain provided by the third-party company.