This utility allows you to check the IP address each domain in your WHMCS system is pointing to. This allows you to easily see which domains are no longer pointing at your servers and therefore identify clients that may no longer be using your service in order to free up resources.
It can be found under Utilities > Domain Resolver. To use simply select which server to check, or select "Check All" to check all of them and click Run Check >> Domains which do not resolve to your server will be highlighted in red, the domain and client name are clickable enabling direct navigation to any account in question. Mass tools can be found at the bottom of the page to email or terminate selected accounts.
Warning: Accounts using a dedicated IP may incorrectly show up as not being pointed to the expected server