Setting up a CNAME record for any one of the domain addresses or subdomains that you've got within a hosting account will enable you to forward 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 address it's being redirected to. In this light, you can't set up a CNAME record to redirect your domain name to a third-party provider and retain a working email service with the first provider. Also, it is essential to know that a CNAME record is always a string of words and not a number as it's commonly confused with the A record of the Internet domain being forwarded. One of the major uses of a CNAME record is to direct a domain name which you own through one provider to the servers of another provider assuming you have created a website with the latter. By doing this, the site will appear under your own domain, not under some subdomain provided by the third-party provider.