Creating a CNAME record for any one of the domains or subdomains you have within a hosting account will allow you to redirect it to a different domain/subdomain. The forwarded domain address will lose all its records - A, MX and so forth, and will take the records of the domain it is being pointed to. In this light, you simply can't set up a CNAME record to forward your domain name to a third-party provider and retain a working email service with the first provider. Additionally, it is important to note that a CNAME record is always a string of words and never a number as it's commonly mistaken for the A record of the domain name being forwarded. One of the primary uses of a CNAME record is to point a domain you own through one provider to the servers of another provider in case you have set up a website with the latter. That way, the website will appear under your own domain address, not under some subdomain provided by the third-party provider.