Setting up a CNAME record for any of the domain addresses or subdomains that you have in a hosting account will allow you to direct it to a different domain/subdomain. The forwarded domain address 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 set up a CNAME record to redirect your domain to a third-party provider and maintain a functional e-mail service with the first provider. Additionally, it is important to note that a CNAME record is always a string of words rather than a number as it is frequently wrongly identified as the A record of the domain name being forwarded. One of the major uses of a CNAME record is to forward a domain name you own through one company to the servers of another provider in case you have created 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 company.