For SMTP routes add a public IP address or Mailhost name as a default route that can be used for all of your domains. When you add a route, the route must pass technical checks before we register the route for your organization's use. After you add an SMTP inbound route, Requested Inbound Routes lists the routes we need to check before registration.
For public hosted cloud routes add the Google Apps Email or Microsoft® Office 365™ mailhost name or IP address, indicated by Microsoft or Google, as default routes that can be used for your hosted email domains.
You can set up default routes for all of your registered domains and then override these defaults with custom routes for each domain.