Editing your default branding domain is the first step in working with branding domains.
Make sure you’ve set up a CNAME in your DNS before you add your branding domains in Marketo.
Go to Admin and click Email.
In the Branding Domains table, select the generic domain and click Edit to change it to your company’s branded domain.
You can’t add an additional domain until you’ve first edited the generic domain.
Enter the name of the your default domain and click Save.
Now, you can add any additional branding domains you need.