# SpacePost

> SpacePost is a Resend-compatible email API for developers, built on AWS SES. Same paths, request/response shapes, error format and webhook signing as the Resend API. Base URL: https://api.spacepost.dev. Auth: `Authorization: Bearer sp_live_...`. Docs: https://docs.spacepost.dev

Key facts:
- Send: `POST /emails` (to/cc/bcc up to 50 each, subject max 998 chars, html or text required, attachments up to 50, tags, headers, scheduled_at up to 30 days), `POST /emails/batch` (max 100). Returns `{ "id": "<uuidv7>" }`.
- Errors: `{ "statusCode": 422, "name": "validation_error", "message": "..." }`.
- Rate limit: 10 req/s per team (25 on Scale), headers `ratelimit-limit/remaining/reset`, `retry-after` on 429.
- Idempotency: `Idempotency-Key` header (1-256 chars, 24h) on POST /emails and /emails/batch.
- Pagination: `limit` (1-100, default 20), `after`, `before` (ids), newest first, `{ object: "list", has_more, data }`.
- Test addresses: delivered@, bounced@, complained@, delayed@test.spacepost.dev. Test sender: onboarding@test.spacepost.dev (only to team members and test addresses).
- Webhooks: Standard Webhooks signing (`webhook-id`, `webhook-timestamp`, `webhook-signature`; `svix-*` duplicates). Events: email.sent, delivered, delivery_delayed, bounced, complained, opened, clicked, failed, scheduled, suppressed. Payload is Resend-shaped: `{ type, created_at, data: { email_id, from, to, subject, created_at, broadcast_id?, tenant_id?, tags? (object), plus bounce | click | open | failed | suppressed per event } }`.
- SDK: `npm i @spacepost/node`; `new SpacePost(process.env.SPACEPOST_API_KEY)`; methods return `{ data, error }`.
- Resend SDK works unchanged with `RESEND_BASE_URL=https://api.spacepost.dev` or `new Resend(key, { baseUrl })`. SpacePost-only fields such as `tenant_id` are dropped by its `emails.send`; use `resend.post("/emails", { ..., tenant_id })` or `@spacepost/node`.
- Platform mode (tenants): your own customers, each with isolated SES reputation, own bounce/complaint guard, pause switch and optional daily cap. `POST /tenants {name, external_id?, daily_limit?}`, `GET /tenants`, `GET|PATCH|DELETE /tenants/{ref}` (`ref` = our id or your external_id; delete is 422 while the tenant has domains), `POST /tenants/{ref}/pause {reason?}`, `POST /tenants/{ref}/unpause` (403 for reputation pauses unless the team is trusted). Needs a full_access key.
- `tenant_id` (our id or external_id) is optional on `POST /emails`, items of `POST /emails/batch` and `POST /domains`. A tenant-owned domain implies its tenant; a team-level domain may send for any tenant; a conflicting `tenant_id` is 422; a paused tenant is 403 `sending_paused`; a tenant over `daily_limit` is 429 `daily_quota_exceeded`. Emails, domains and webhook `data` carry `tenant_id`.
- SMTP: smtp.spacepost.dev, port 25976 with STARTTLS (required before AUTH; implicit TLS on 465 is not offered yet), user `spacepost`, password = API key.
- Never put API keys in browser code.

## Getting started
- [Introduction](https://docs.spacepost.dev/getting-started/introduction/): what SpacePost is and how it compares
- [Quickstart](https://docs.spacepost.dev/getting-started/quickstart/): key, first email, domain
- [Migrating from Resend](https://docs.spacepost.dev/getting-started/migrating-from-resend/): parity table and differences
- [Node.js](https://docs.spacepost.dev/getting-started/quickstarts/nodejs/), [Next.js](https://docs.spacepost.dev/getting-started/quickstarts/nextjs/), [Python](https://docs.spacepost.dev/getting-started/quickstarts/python/), [Go](https://docs.spacepost.dev/getting-started/quickstarts/go/), [PHP](https://docs.spacepost.dev/getting-started/quickstarts/php/), [Ruby](https://docs.spacepost.dev/getting-started/quickstarts/ruby/), [Rust](https://docs.spacepost.dev/getting-started/quickstarts/rust/), [cURL](https://docs.spacepost.dev/getting-started/quickstarts/curl/), [SMTP](https://docs.spacepost.dev/getting-started/quickstarts/smtp/)

## Sending
- [Send an email](https://docs.spacepost.dev/sending/send-email/)
- [Batch sending](https://docs.spacepost.dev/sending/batch/)
- [Scheduling](https://docs.spacepost.dev/sending/scheduling/)
- [Attachments](https://docs.spacepost.dev/sending/attachments/)
- [Tags](https://docs.spacepost.dev/sending/tags/)
- [Custom headers](https://docs.spacepost.dev/sending/headers/)
- [Idempotency keys](https://docs.spacepost.dev/sending/idempotency/)
- [React Email](https://docs.spacepost.dev/sending/react-email/)
- [Testing](https://docs.spacepost.dev/sending/testing/)

## Domains
- [Adding and verifying](https://docs.spacepost.dev/domains/adding-and-verifying/)
- [DMARC](https://docs.spacepost.dev/domains/dmarc/)
- [Open and click tracking](https://docs.spacepost.dev/domains/tracking/)
- [Custom return path](https://docs.spacepost.dev/domains/return-path/)
- [Troubleshooting](https://docs.spacepost.dev/domains/troubleshooting/)

## Webhooks
- [Overview](https://docs.spacepost.dev/webhooks/overview/)
- [Event types](https://docs.spacepost.dev/webhooks/event-types/)
- [Verifying signatures](https://docs.spacepost.dev/webhooks/verifying/)
- [Retries](https://docs.spacepost.dev/webhooks/retries/)

## Platform mode
- [Platform mode (tenants)](https://docs.spacepost.dev/platform/tenants/): create tenants, tenant-owned vs team-level domains, send for a tenant, pause, caps, webhooks

## Audiences and broadcasts
- [Contacts](https://docs.spacepost.dev/audiences/contacts/)
- [Broadcasts](https://docs.spacepost.dev/audiences/broadcasts/)
- [Personalization](https://docs.spacepost.dev/audiences/personalization/)
- [Unsubscribe](https://docs.spacepost.dev/audiences/unsubscribe/)

## Deliverability and account
- [Best practices](https://docs.spacepost.dev/deliverability/best-practices/)
- [Bounces, complaints and suppressions](https://docs.spacepost.dev/deliverability/bounces-and-complaints/)
- [Account sandbox](https://docs.spacepost.dev/deliverability/sandbox/)
- [Automatic pausing](https://docs.spacepost.dev/deliverability/auto-pausing/)
- [Account verification and sending limits](https://docs.spacepost.dev/account/verification-and-limits/)
- [Plans and quotas](https://docs.spacepost.dev/account/plans-and-quotas/)
- [Security and API keys](https://docs.spacepost.dev/account/security/)

## API and tools
- [API introduction](https://docs.spacepost.dev/api/introduction/)
- [Errors](https://docs.spacepost.dev/api/errors/)
- [Rate limits](https://docs.spacepost.dev/api/rate-limits/)
- [Pagination](https://docs.spacepost.dev/api/pagination/)
- [API reference](https://docs.spacepost.dev/api-reference/)
- [OpenAPI spec](https://api.spacepost.dev/openapi.json)
- [Node.js SDK](https://docs.spacepost.dev/tools/node-sdk/)
- [CLI](https://docs.spacepost.dev/tools/cli/)
- [MCP server](https://docs.spacepost.dev/tools/mcp/)
- [SMTP relay](https://docs.spacepost.dev/tools/smtp/)

## Full text
- [llms-full.txt](https://docs.spacepost.dev/llms-full.txt): key pages concatenated