Setting up a CNAME record for each of the domain addresses or subdomains that you've got in a hosting account will enable you to forward it to a different domain/subdomain. The forwarded domain will lose all of its records - A, MX etc, and will take the records of the domain it is being directed to. In this light, you can't set up a CNAME record to redirect your domain to a third-party company and keep a working e-mail service with the first hosting provider. It's also important to note that a CNAME record is always a string of words and not a number as it is generally wrongly identified as the A record of the Internet domain being redirected. One of the major uses of a CNAME record is to forward a domain name you own through one provider to the servers of another company if you have created a site with the latter. That way, the site will appear under your own domain, not under some subdomain provided by the third-party provider.