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Glossary · Published 2026-09-29 · AgentiSend team

Preflight

Preflight: A check that reports what a send would do, without sending it or recording a hold.

POST /emails/preflight runs the same gates as a send and does not accept the message. It does not charge the budget and it does not file an approval. Use it, or a simulator address, before a sending domain is verified.

The reply names the gate that would refuse the real send. A preflight that passes is not a delivery.

Related terms

  • Simulator address — An address that accepts a send, costs nothing, and delivers to nobody.
  • Sending domain — A domain you verify, then send from. An unverified From is refused.