Group most deferred domains by the top level domain
Currently the most deferred domains chart shows domains separated by their sub-domains. However the top level domain is what determines the policy in most cases, so the subdomain for the specific MX server which has deferred mail is is less important than the top level domain in use, such as icloud.com. therefore group the domains in this chart by the top level domain and display them.
As an administrator When I use the most deferred domains chart Then I should see only top level domains