Setting up a CNAME record for each of the domains or subdomains that you have in the hosting account will enable you to direct it to a different domain/subdomain. The forwarded domain address will lose all of its records - A, MX and so on, and will take the records of the domain address it's being directed to. In this light, you simply can't set up a CNAME record to point your domain name to a third-party company and keep a working e-mail service with the first provider. It's also essential to know that a CNAME record is always a string of words rather than a number as it's commonly wrongly identified as the A record of the domain name being forwarded. One of the main uses of a CNAME record is to direct a domain which you own through one company to the servers of another company in case you have set up an Internet site with the latter. This way, the Internet site will appear under your own domain, not under some subdomain provided by the third-party company.