Questions · Updated 2026-09-23

How do I test email sending without delivering anything?

Test email sending without delivering anything by addressing every recipient at simulator.agentisend.com, or by calling POST /emails/preflight, which runs every send check and does not send.

Test email sending without delivering anything in either of two ways. Address every recipient at simulator.agentisend.com and call POST /emails: the operation summary says those addresses cost nothing and reach nobody, and Domains and DNS says nothing leaves and any well-formed From is accepted. Or call POST /emails/preflight, whose summary is that it runs every send gate without sending and that the report matches what POST /emails would do.

The simulator

POST /emails returns simulated. That field is true when every recipient is a simulator address: the send is accepted and it costs nothing. One recipient anywhere else and simulated is false, and that send is delivered. GET /emails/{id} is the stored message either way.

curl -sS -X POST https://api.agentisend.com/emails \
  -H "Authorization: Bearer $AGENTISEND_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{"from":"billing@yourdomain.com","to":"customer@example.com"}'
201
{
  "id": "9c8f8f0e-3d1a-4d3f-9a1e-2b7c1a0f5e42",
  "simulated": true,
  "warnings": []
}
Response

Use an address such as success@simulator.agentisend.com. The domain is the rule. The local part is not.

Preflight

POST /emails/preflight takes the same body as POST /emails and returns ok, simulated, error, and checks. It does not create a message. When ok is false, error carries the same code, message, and fix the send would have returned.

curl -sS -X POST https://api.agentisend.com/emails/preflight \
  -H "Authorization: Bearer $AGENTISEND_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{"from":"billing@yourdomain.com","to":"customer@example.com"}'
201
{
  "checks": "string",
  "error": "string",
  "ok": true,
  "simulated": true
}
Response

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