CNAMEs can only be set for domains that are registered with 1&1. It is recommended that you read the Explanation of CNAMEs first.
If using a CNAME, all DNS settings configured through the 1&1 Control Panel will be discarded. A CNAME can be thought of as a kind of pointer for DNS. Instead of specifying DNS settings for a domain in the Control Panel, using a CNAME indicates that the DNS settings for the domain should be exactly the same as the DNS settings for the CNAME address.
Enter the CNAME address in the Alias text box (The CNAME cannot exceed 38 characters).
Check the box to acknowledge that you are aware all current DNS settings will be disabled by using a CNAME instead.
Click the OK button to continue.
Please note that all DNS changes (such as a CNAME) may take 24-48 hours until the changes are recognized by all servers/computers on the Internet.