Setting up a CNAME record for any one of the domain names or subdomains that you have within a hosting account allows you to direct 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 address it's being redirected to. In this light, you simply can't set up a CNAME record to direct your domain to a third-party company and maintain a working email service with the first hosting provider. It is also important to note that a CNAME record is always a string of words and not a number as it is commonly confused with the A record of the Internet domain being forwarded. One of the primary uses of a CNAME record is to direct a domain address you own through one company to the servers of another company assuming you have set up a site with the latter. This way, the Internet site will appear under your own domain, not under some subdomain provided by the third-party provider.