By classifying your own domains, OnDOMAIN will not only show you possible threat at the Top Level Domains, but also at the Sub Domains Level.
To get to it. Click on a domain that you own and scroll down to the subdomains section. If no subdomains are detected by OnDOMAIN then it won't be shown.
Here is an example:
Details of vulnerability checks:
CNAME: Does this domain point to another Domain name using a cname? (OnDOMAIN will check where it is pointed to and alerts you if it is not associated to anything or no longer under your control).
Green Dot: No CNAME/Pointed to an IP.
Red Dot: Dangling CNAME - Not pointed to anything.
SPF: Is the subdomain setup to send Emails?
MX: Is the subdomain setup to receive Emails?
IP reputation: Checks all IPs associated with the subdomain against threat feeds to make sure there are no issues.