It can be anything! An apex, subdomain, or even a URL.
Domain Name: postmaster.sked.aiDomain Status: No Object Found>>> Last update of WHOIS database: 2024-09-22T09:22:21.859Z <<<
Domain Name: postmaster.sked.ai
Domain Status: No Object Found
>>> Last update of WHOIS database: 2024-09-22T09:22:21.859Z <<<