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Sending

One request, or the mailer you already have.

A REST API with idempotency keys and honest rate limits, plus an SMTP relay that accepts whatever you are already using. Both take the same path and leave the same evidence.

Start sendingAPI reference
Sending

REST API, SMTP relay, scheduling, two streams.

OutSend's REST API and SMTP relay: fields, idempotency, rate limits, streams, and scheduling.

A REST API that fits on one page

POST to one endpoint with from, to, subject, and a body. Optional cc, bcc, replyTo, custom headers, and scheduling. The response gives you an id, which is how you pull the trace back later.

  • Idempotency that actually helps · Send an Idempotency-Key header and the result is cached for 24 hours. Your retry logic can be as aggressive as your network is unreliable without ever duplicating a message.
# Send a transactional email
curl -X POST https://app.getoutsend.com/api/v1/emails \
  -H "Authorization: Bearer $OUTSEND_API_KEY" \
  -H "Idempotency-Key: order-8421" \
  -d '{
    "from": "Acme <hello@mail.acme.com>",
    "to": ["maya@example.com"],
    "reply_to": "support@acme.com",
    "subject": "Your order is on its way",
    "html": "<p>Hi Maya, it shipped!</p>"
  }'

An SMTP relay for what you already have

Host, port 2587, STARTTLS, username outsend, password your API key. Nodemailer, ActionMailer, Django, or anything else that speaks SMTP works unchanged — and produces exactly the same events as the API.

  • Rate limits you can read · 60 requests a minute and 1,000 an hour per key, returned as a 429 with a sentence explaining it. We would rather refuse loudly than accept a message and quietly drop it.

Two streams, two suppression lists

Transactional and broadcast are kept apart, each with its own suppression list. Someone unsubscribing from your newsletter never stops their password reset from arriving.

  • Scheduling · Pass scheduled_at on a send, or send_at on a campaign. Scheduled mail sits in the queue where you can see it, and can be cancelled before it goes.
What you can inspect

Go and check.

Documentation

  • The exact request that produced a message, including the idempotency key.
  • Whether a message came in over the API or SMTP — source is recorded on every send.
  • Scheduled mail sitting in the queue before it goes out.
  • The provider's response to every delivery attempt.
  • API reference
  • SMTP relay
  • Quickstart

We would rather refuse loudly than accept a message and quietly drop it.

Rate limits you can readSending

The rest of the platform

Send one message.

The quickstart ends by having you read a real trace, which is the only part of this that needs explaining.

Start sendingOr self-host it

Open core · never venture-backed · operated by Martin Business Consultants