Postbag documentation
Give a Form somewhere dependable to go. Start before signup, use the complete API, or run the same open-source product yourself.
Postbag is the open-source form backend built for agents. A website posts to a stable Form URL. Postbag saves every Submission first, then Routes it to email, Telegram, a webhook, or another Destination. Add a secret when the receiver should verify an HMAC signature.
An agent can create and test a bounded sandbox Form before you sign up. When the work is ready to keep, claim the same Form, add a Destination and Route, and send a new Submission to verify Delivery.
Choose your starting point
Let your agent handle it
Install the Postbag skill, then give the agent the job:
npx skills add faahim/postbag --skill postbagThe agent can create a sandbox, wire the returned submit URL into the site, send a test, and prove Postbag stored it. The sandbox lasts 24 hours and accepts up to five test Submissions. No account or API key is needed for that first proof.
Start from an account
If you already have a manage-scoped API key, POST /v1/quickstart creates a Form and returns its submit URL, embed snippets, verification call, and next steps. Include at least one email, Telegram, or webhook Destination if you want the quickstart to create a Route and produce Deliveries.
Run Postbag yourself
Postbag is one application image plus Postgres 16. OAuth providers are optional. Email-code authentication and email Delivery need a configured mail provider, while the rest of the product remains available without social login.
The one idea
The database makes it correct; events make it fast. A Submission is a row before it is anything else. Delivery runs through a durable outbox. Spam, quota, and rate-limit outcomes are stored with a status instead of disappearing.
A Form can receive without a Route. It cannot deliver until a Destination and Route connect it to somewhere onward. That distinction is deliberate: receiving and keeping data must not depend on a provider being available.
Find the exact answer
- Submit endpoint covers content types, control fields, browser origins, and response shapes.
- API overview covers authentication, resources, pagination, idempotency, and errors.
- Routing explains how Forms and Streams connect to Destinations.
- Schemas explains immutable versions, observe mode, and Drift.
- Webhook signatures includes verification examples for Node, Python, and Go.
- Architecture and Security explain the outbox, tenancy, and trust boundaries.
- Error codes maps every API error to a concrete recovery step.
Documentation for agents
The running server describes itself. GET /llms.txt is the short onboarding document and GET /openapi.json is generated from the live route definitions.
Every documentation page also has a Markdown twin. Send Accept: text/markdown or append index.md to its path. /llms-full.txt concatenates the complete documentation set for a larger context window.
