I am trying to understand how I can configure my .NET website to display each domain or groups of domains as Applications in the New Relic RPM console.
There is an article explaining here how to do it for PHP https://newrelic.com/docs/php/per-directory-settings
At this time, the .NET agent doesn't support differentiating which application to report to based on the hostname of each request.
UPDATE December 2017: Please go to the URL above and vote for the feature if you think this feature would be useful.