Use haveibeenpwned.com to check an email address against the index of multiple data breaches (and dumps that aren't really breaches). The site used to let a domain security contact search for hits on their domain, but that is now a paid freemium feature that can cost quite a bit (fair value though).

Have I Been Pwned: Check if your email has been compromised in a data breach

Have I Been Pwned allows you to search across multiple data breaches to see if your email address or phone number has been compromised.