The pattern behind most of it
A real customer's email address resolves, has mail servers, and belongs to a provider they actually use. A throwaway signup usually has at least one of: a disposable-provider domain, a domain that doesn't exist or has no mail servers at all, or a plus-alias or typo variant of a real address used to dodge a one-per-email limit. None of these need a human to spot - they're exactly what a verification check surfaces automatically.
Where to actually check
| Situation | Where to check |
|---|---|
| Your signup or checkout form, before the account/order is created | Real-time check via the API, or the embeddable widget on the form itself |
| A batch of existing signups or orders you already suspect | Paste them into the free list checker |
| Leads coming in from a form, integration or CRM | Bulk verify on a schedule via the API or an integration |
What this won't do
A disposable or nonexistent address is a strong, cheap signal - it is not a fraud score. A fraudster using a real Gmail address to test a stolen card will sail straight through an email check. If card-testing or payment fraud specifically is the problem, pair this with your payment processor's own fraud signals (card velocity, AVS, device fingerprinting) rather than expecting email checks alone to carry that weight.