my domain is http://emissary.zxq.net
Changing CNAME record
To use the custom URL mail.emissary.zxq.net, you must change the CNAME record with your domain host.
Sign in to your domain hosting service.
Navigate to your DNS Management page. The location and name of this page will vary by host, but can generally be found in Domain Management or Advanced Settings.
Find the CNAME settings and enter the following as the CNAME value or alias:
Set the CNAME destination to the following address:
ghs.google.com