There are two options for this, using a CNAME or adding MX records manually.We recommend adding the MX records directly to your account.
Once you are on the page you can click the custom domains button to add your domain name to the address.
This may mean that you have to update the records if Cloud Mailin ever changes it's defaults however, using a CNAME can cause issues in some edge cases so it's generally worth the overhead.
CNAME Records make management of your domain much easier, your entire domain will be given the DNS records that we specifiy for clients.and will be updated whenever we change these entries automatically.
The Custom Domain feature allows you to use Cloud Mailin to receive all email for your domain.
With Custom Domains you can create a DNS entry in your own domain name to allow Cloud Mailin to accept all email on that domain and forward it onto your website just like your regular Cloud Mailin address.
Authentication is a way to prove an email isn't forged.