Creating a CNAME record for any one of the domain names or subdomains you've got in the hosting account allows 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's being redirected to. In this light, you cannot create a CNAME record to forward your domain to a third-party provider and keep a working email service with the first hosting company. Additionally, it is very important to know that a CNAME record is always a string of words and never a number because it is commonly confused with the A record of the domain name being forwarded. One of the major uses of a CNAME record is to point a domain address which you own through one provider to the servers of another company in case you have set up a website with the latter. This way, the site will appear under your own domain name, not under some subdomain provided by the third-party provider.