Introduction
What MillionSend is and how the pieces fit together.
MillionSend is the open-source email platform. Send one. Send a million.
Use it two ways, running the same code either way:
- MillionSend Cloud — the hosted service at
millionsend.com. Sign up, verify a domain, send.
API at
api.millionsend.com. - Self-hosted — run it on your own infrastructure with Docker Compose, sending through your own AWS SES account. See Self-hosting.
Both share one dashboard, one HTTP API, and the same SDKs — these docs cover both, and the Cloud / Self-hosted tabs you'll see on some pages remember your choice. Around the sending core you get a dashboard, an HTTP API, SDKs, webhooks, contacts, broadcasts, and an SMTP relay.
Resend-compatible API
The HTTP API is wire-compatible with Resend: same request and response shapes, same error format. Official Resend SDKs honor a configurable base URL, so migrating an existing integration means changing two environment variables — the API key and the base URL — not rewriting your code. MillionSend also ships its own SDKs for nine languages that mirror the Resend SDK shapes.
One deliberate difference: contacts are team-global. There is no "audiences" concept — every contact belongs to your team directly, and you target subsets with segments (saved filters) and topics (opt-in categories). See Contacts.
What's included
| Area | Notes |
|---|---|
| Emails API | Send, batch, get, cancel scheduled sends. Idempotency via the Idempotency-Key header. |
| Contacts | Team-wide contacts with subscribe state, custom properties, and CSV import. |
| Segments | Saved filters over contacts, usable as broadcast targets. |
| Topics | Granular subscription categories wired into the hosted unsubscribe page. |
| Broadcasts | Compose, schedule, and send to all contacts, a segment, or a topic. |
| Templates | Reusable templates with per-contact merge fields. |
| Domains | Guided DNS verification, BYODKIM, per-domain tracking and TLS settings. |
| Webhooks | Standard Webhooks signatures, per-endpoint event selection, delivery log. |
| Suppressions | Hard bounces and complaints suppressed automatically. |
| One-click unsubscribe | RFC 8058 List-Unsubscribe headers plus a hosted unsubscribe page. |
| SMTP relay | Drop-in SMTP on port 2587, authenticated with an API key. |
| Metrics | Daily sends with bounce and complaint rates tracked against SES thresholds. |
| Dashboard | Full dashboard in English and Brazilian Portuguese. |
Architecture at a glance
MillionSend sends through AWS SES — on Cloud that's managed for you; on a self-hosted deployment it's your own SES account, so you keep SES's deliverability and pricing. A self-hosted deployment is two containers:
- Postgres — the only datastore. The job queue (pg-boss) runs on it too; there is no Redis.
- App container — runs the API (port 3001), the background worker, and the
web dashboard (port 3000). An optional third container runs the SMTP relay
(port 2587). Processes can also be split one-per-container with the
PROCESSenvironment variable.
Email bodies are encrypted at rest (AES-256-GCM envelope encryption) and purged after a retention window. Delivery events (bounces, complaints, deliveries) flow back from SES — on Cloud automatically; self-hosted through SNS into an SQS queue the worker long-polls, plus a push to your host when it has a public HTTPS URL.
Where to go next
- Quickstart — from zero to your first email in a few minutes, on Cloud or your own instance.
- Self-hosting — the full deployment reference.
- API reference — generated from the server code, always in sync.
For AI agents
Every documentation page is available as raw markdown by appending .md to
its URL (or sending Accept: text/markdown). /llms.txt is a
machine-readable index, /llms-full.txt is the entire
documentation in one file, and /openapi.json is the OpenAPI
3.1 spec generated from the API's code.
License
The platform is AGPL-3.0. SDKs are published separately under MIT.