Creating a CNAME record for each of the domain names or subdomains that you've got 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 and so forth, and will take the records of the domain it's being pointed to. In this light, you can't set up a CNAME record to redirect your domain name to a third-party provider and retain a working e-mail service with the first provider. It's also very important to know that a CNAME record is always a string of words rather than a number because it is often wrongly identified as the A record of the domain address being redirected. One of the main uses of a CNAME record is to direct a domain that you own through one provider to the servers of some other company if you have set up a site with the latter. That way, the website will appear under your own domain, not under some subdomain provided by the third-party provider.