Setting up a CNAME record for any of the domain addresses or subdomains you've got in the hosting account will permit 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's being redirected to. In this light, you simply can't set up a CNAME record to direct your domain to a third-party provider and retain a working email service with the first provider. It's also very important to know that a CNAME record is always a string of words and never a number as it is regularly confused with the A record of the domain address being forwarded. One of the major uses of a CNAME record is to point a domain name which you own through one company to the servers of another company when you have set up an Internet site with the latter. This way, the website will appear under your own domain name, not under some subdomain provided by the third-party provider.