Creating a CNAME record for each of the domain names or subdomains that you've got in a hosting account allows you to redirect it to a different domain/subdomain. The forwarded domain name will lose all of its records - A, MX and so on, and will take the records of the domain it's being directed to. In this light, you can't set up a CNAME record to point your domain to a third-party provider and retain a working e-mail service with the first provider. Additionally, it is essential to know that a CNAME record is always a string of words and never a number as it is often confused with the A record of the domain address being redirected. One of the main uses of a CNAME record is to direct a domain address which you own through one provider to the servers of some other provider in case you have created a site with the latter. In this way, the Internet site will appear under your own domain name, not under some subdomain provided by the third-party provider.