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Open email infrastructure · API · CLI · MCP

Email for agents and humans.

Infrastructure you can read, run, and audit — with the provider's own response behind every message, so a person or a machine can see where it went and why.

Start sendingRead the docs

$9.99/mo · 7-day free trial · or run it yourself, free

Sending in production for

  • Behnke Logistics
  • Hello Storage
  • Biofuse
  • Kalamazoo Excavation
  • Mule Box Portable Storage
  • The Foundry Kalamazoo
  • Treystar

and more

  • Emails a day, in productionMillions
  • Event types, all queryable8
  • Signed webhook events6
  • Auditable core, managed convenienceOpen + cloud
01 · Agents

Agents are first-class citizens.

Software that has to prove its own work needs more than a one-word verdict. An agent cannot act on “delivered” — it needs the evidence, the uncertainty, and a gate before it changes anything that matters.

API, CLI, and MCP with verifiable outcomes.

So all three surfaces are built to the same rule: return what happened, what it was derived from, and what you could not determine. Reading and diagnosing run freely. Changing things is gated on a human.

  • API · World-class primitives. Stable, composable endpoints for sending, events, domains, and reputation controls — with idempotency keys, readable errors, and the provider's response on every event.
  • CLI · Operational leverage. Scriptable setup, inspection, replay, migration, and diagnostics. Everything you can do by clicking, available to a shell script, a runbook, or a CI job.
  • MCP · Native agent access. An MCP server agents connect to directly: send, inspect traces, explain failures, and propose remediation with structured, explainable outcomes.
How the agent surfaces work
02 · Start sending

One request, or the SMTP settings you already have.

A REST API with idempotency keys and honest rate limits, plus an SMTP relay that accepts whatever mailer you are already using. Verify a domain, send, then go read the trace.

Replay-safe, and limits you can read.

Retries do not duplicate mail, and a limit is never a silent drop.

  • Idempotency · Replay-safe for 24 hours. Retries do not duplicate mail.
  • Rate limits · 60/min and 1,000/hour per key — returned as a 429 you can read, never a silent drop.
Read the docs
# 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>"
  }'

Martin Business Consultants built OutSend for its own production sending, then productised it. It is funded by customers paying for cloud and support — which is a slower way to build a company and a much better way to build infrastructure.

Show your work.Martin Business Consultants
04 · Observable sending

“Delivered” is a summary. We keep the sentence it came from.

Acceptance is not delivery, and an aggregate percentage cannot tell you which. Every event OutSend records keeps the provider's own response — the SMTP code, the reason, the reporting host — so a person or an agent can explain what happened rather than guess.

Six events, one schema

Each endpoint gets its own HMAC secret and its own delivery log — attempts, response codes, response bodies. When a webhook fails, you can see that too.

  • email.delivered
  • email.bounced
  • email.opened
  • email.clicked
  • email.complained
  • email.unsubscribed
05 · Reputation sovereignty

Your reputation is yours. No neighbour can burn it.

On a shared pool, the worst sender sets everyone's ceiling. OutSend scores reputation per domain and per workspace, and when a sender crosses the line we stop them — automatically, before their behaviour becomes your bounce rate.

  • Sending runs on AWS-backed infrastructure with your own verified identity: DKIM, SPF, and DMARC against your domain, in the region you choose.
How domain verification works
03 · The standard

Five things a sending platform should be able to prove.

Not five features. Five claims we are willing to be held to, each with something you can go and check.

06 · Open source

Open source is the exit plan.

Read the code, run it yourself, or choose the convenience of cloud. The point of a portable control plane is that leaving is a documented path rather than a threat you never get to test.

  1. 01

    Open core

    The product itself is inspectable and self-hostable — not a lead magnet bolted onto a closed service. Contributions improve the same control plane our cloud runs.

  2. 02

    Managed cloud

    You pay for hosting, managed deliverability, operations, and support — for time, not for access. There is no feature we removed from the code to sell it back.

  3. 03

    Revenue funds openness

    Cloud and support sustain the core indefinitely. No venture capital means no acquisition clock, and no quarter where reliability loses to growth theatre.

Self-hosting guideView the source
07 · Where trust is expensive

We started where getting it wrong is worst.

OutSend runs millions of production emails a day across workloads where an unexplained failure is not an inconvenience. Same trust stack, three versions of the same enemy.

Highest trust barHIPAA-compliant medicalEnemyBlack-box handling of sensitive communications, thin auditability, and unclear operational responsibility.MessageAuditable, compliant, observable sending. Every event explainable, infrastructure inspectable, incidents disclosed.Read moreMission-sensitiveNonprofitsEnemyPer-email pricing and growth economics that tax mission-driven communication.MessageA sustainably priced platform whose cloud revenue funds an open core — without turning the mission into a margin target.Read moreTime-sensitiveLogistics & shippingEnemyDowntime and opaque delivery that can interrupt the real-world movement of goods.MessageObservable, SLA-backed infrastructure with per-provider evidence, incident clarity, and agent-ready remediation.Read more

We name the companies happy to be named, and say nothing at all about the regulated workloads. Trust-sensitive mail does not become case-study material.

08 · The long game

Never venture-backed. No acquisition clock.

There is no exit clock here, and no quarter where reliability loses to growth. That is not a grievance about venture capital; it is a statement about what our incentives reward.

  • Agents are first-class citizens. API, CLI, and MCP with verifiable outcomes.
  • Show your work. See where every email went — and why.
  • Your reputation is yours. No neighbour can burn it. No vendor owns it.
  • Open source is the exit plan. Read the code, run it yourself, or choose cloud.
  • We're playing the long game. Never VC. Paid alignment.
Read the manifesto
Our transparency methodologyThe method, before the numbers.Get started$9.99/mo · 7-day free trial · or run it yourself, free

Ready to see where your email goes?

Seven days free. No card to start, and everything we claim is checkable.

Start sendingOr self-host it

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