Creating a CNAME record for any of the domain names 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 on, and will take the records of the domain name it is being redirected to. In this light, you cannot create a CNAME record to forward your domain name to a third-party provider and maintain a working email service with the first hosting provider. It is also very important to know that a CNAME record is always a string of words and not a number because it is regularly wrongly identified as the A record of the Internet domain being redirected. One of the major uses of a CNAME record is to direct a domain you own through one company to the servers of another provider if you have set up a website with the latter. By doing this, the website will appear under your own domain, not under some subdomain provided by the third-party provider.