Setting up a CNAME record for any one of the domain addresses or subdomains that you've got in a hosting account allows you to direct it to a different domain/subdomain. The forwarded domain will lose all of its records - A, MX and so on, and will take the records of the domain address it is being redirected to. In this light, you can't set up a CNAME record to forward your domain to a third-party company and keep a working e-mail service with the first hosting provider. It is also important to note that a CNAME record is always a string of words rather than a number as it is often mistaken for the A record of the domain being redirected. One of the major uses of a CNAME record is to point a domain you own through one company to the servers of another company when you have created a website with the latter. In this way, the website will appear under your own domain name, not under some subdomain provided by the third-party company.