A catch-all domain accepts mail for addresses whether or not the individual mailbox can be confirmed. It is not the same as deliverable, and it is not automatically undeliverable.

Why catch-all changes the answer

During an SMTP check, a catch-all server behaves as if many different recipients are acceptable. That prevents a verifier from using the server response as proof that one specific mailbox exists.

Treat it as risk, not certainty

The appropriate action depends on the value of the contact, the quality of the source, your sending reputation, and the cost of a bounce. Preserve the catch-all signal and combine it with domain and contact context.

  • Prioritize known, engaged contacts
  • Use smaller sending batches for uncertain data
  • Avoid presenting catch-all as a confirmed mailbox

How MailTooth reports it

Deepcheck reports catch-all as mailbox-level evidence and marks the outcome as risky rather than inventing certainty. The result stays explicit so your workflow—not the verifier—makes the final business decision.

Put the framework into practice.

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