Postbag documentation

Postbag is a form backend that routes. Websites POST to a submit URL; Postbag stores every submission durably and delivers it to email, Telegram and signed webhooks according to routes you configure. It is multi-tenant, self-hostable, and agent-native: everything a human can do in the dashboard, an agent can do with an API key.

The one idea

The database makes it correct; events make it fast. A submission is a row before it is anything else. Delivery is an outbox drained by a worker. Spam, quota and rate-limit outcomes are stored with a status, never dropped.

The three calls that matter

1. GET /v1/me: who am I, which organization, which scopes, what already exists. Call this first with your API key.
2. POST /v1/quickstart: one call to a working, routed form. Idempotent by (project, name). Returns a submit URL, embed snippets and a verification recipe.
3. POST /s/{formId}: submit to a form. No auth. Accepts JSON, urlencoded and multipart (text fields). Pass _test: true to get submission and delivery ids back, so you can poll GET /v1/deliveries/{id} and see sent.

Where to go next

• Quickstart: three minutes to your first email.
• Submit endpoint: every control field, content type and status.
• API overview: resources, conventions, pagination, idempotency, errors.
• Agent guide: the exact flow an agent should follow, and the repo conventions.
• Webhook signatures: verify Postbag-Signature in Node, Python and Go.
• Routing, Schemas, Destinations.
• Architecture, Security, Self-hosting, Error codes.

For agents

The live API describes itself: GET /llms.txt is the onboarding page in Markdown and GET /openapi.json is generated from the route definitions, so it is always current. Every page on this site also has a Markdown twin: request it with Accept: text/markdown, or append index.md to the URL path. The whole documentation set is concatenated at /llms-full.txt.