I am sorry about the delayed response to your topic!
Since these email addresses appear be to be potential bots mass registering in your application you can:
Enable Bot Detection - Dashboard → Security → Attack Protection → Bot Detection. This forcers a captcha challenge when the system detects suspicious behaviour.
Enforce email verification or SMS MFA on Signup - Since these accounts can be potential bots, it will be much harder to register with them while needing to verify the email itself or use multiple numbers for the MFA process.
Enable Suspicious IP Throttling - Security > Attack Protection > Suspicious IP Throttling - If the signup requests originate from the same IP or similar ones, it will block after multiple failed attempts