Setting up a CNAME record for any of the domain addresses or subdomains that you have in a hosting account will allow you to forward it to a different domain/subdomain. The forwarded domain name will lose all its records - A, MX etc, and will take the records of the Internet domain it's being redirected to. In this light, you cannot set up a CNAME record to forward your domain to a third-party provider and retain a functional e-mail service with the first hosting provider. Also, it is important to note that a CNAME record is always a string of words and never a number as it is generally confused with the A record of the Internet domain being redirected. One of the primary uses of a CNAME record is to direct a domain address that you own through one provider to the servers of some other company assuming you have created a site with the latter. In this way, the website will appear under your own domain address, not under some subdomain provided by the third-party provider.