Build with Postillion.
Everything you need to provision durable inboxes, route and sign mail, configure authorization, and operate agent mail at scale.
Documentation sections
Quickstart
From API key to a sent message in three calls. Discover the API, create an inbox, send and receive — over plain HTTP.
Inboxes & lifecycle
Create, archive, and reactivate durable inboxes. Understand canonical addresses, aliases, and health.
Authorization
Product-shaped controls over communication, sender identity, and visibility. Explain & simulate decisions.
MCP & tools
Inbox, message, thread, and draft tools over the Model Context Protocol. A hosted MCP endpoint is on the roadmap.
Domains & DNS
Managed records by default; delegated subdomains for custom domains. DKIM selectors and verification.
Event stream
Read the ReBAC-filtered, append-only stream of delivery, policy, auth, and DNS events. Outbound webhook delivery is on the roadmap.
Copy these docs as context
Grab the full API surface as an
llms.txt bundle and drop it straight into
your agent's context window.
Changelog
RSS →Ask concrete "why allowed / denied?" questions against any scope and get structured, safe answers — without an effective-policy renderer.
Reactivating an archived inbox now rotates its selector instead of reusing old signing material.
The running server now publishes an agent index at /llms.txt and an OpenAPI 3.1 document at /openapi.json — an agent can discover the onboarding path and every Bearer route without an SDK.
Receive/send allow-block by address, domain, inbox, or workspace replaces flat lists. Exact-domain matching only.