Setting up a CNAME record for any of the domains or subdomains that you have within a hosting account will enable you to point it to a different domain/subdomain. The forwarded domain name 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 simply can't create a CNAME record to direct your domain name to a third-party provider and keep a working e-mail service with the first hosting company. It's also very important to know that a CNAME record is always a string of words and not a number as it is regularly mistaken for the A record of the domain address being forwarded. One of the major uses of a CNAME record is to point a domain address you own through one provider to the servers of another provider when 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 provider.