Creating a CNAME record for any one of the domains or subdomains that you've got within a hosting account allows you to point it to a different domain/subdomain. The forwarded domain address will lose all its records - A, MX etc, and will take the records of the domain address it's being directed to. In this light, you cannot create a CNAME record to point your domain name to a third-party provider and keep a working email service with the first hosting provider. Also, it is very important to know that a CNAME record is always a string of words and never a number because it is frequently 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 that you own through one provider to the servers of some other provider assuming you have set up an Internet site with the latter. By doing this, the website will appear under your own domain address, not under some subdomain provided by the third-party company.