We are using many signals or indicators when evaluating domains and e-mails. Anything from domain info, honeypots, registrar information, threat intel, etc.
The “text” and “reason” is basically just a text-based information about why we have flagged the email/domain as invalid, or why it should be blocked.

“Anomalies detected” just means that we found “something” that looks odd. We actually updated that now for test.com, updating the info to it being blacklisted.

The most important field is the “block” value, which is if we suggest you block it or not, either because it’s invalid, or bad/disposable/malicious.