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