Setting up a CNAME record for each of the domain addresses or subdomains that you've got in the hosting account will permit you to forward 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 name it's being pointed to. In this light, you cannot set up a CNAME record to forward your domain name to a third-party company and maintain 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 as it's regularly confused with the A record of the Internet domain being forwarded. One of the primary uses of a CNAME record is to direct a domain name you own through one company to the servers of some other provider if you have set up a website with the latter. That way, the Internet site will appear under your own domain address, not under some subdomain provided by the third-party company.