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PostStack documentation

Guides and API reference for sending, receiving and managing email with PostStack — over HTTP, SMTP, the SDKs or MCP.

Start here#

New to PostStack? This path gets a real email delivered and wired into your app:

  1. Send your first email

    Verify a domain, create a key and send — Quickstart.

  2. Authenticate properly

    Pick the right key permission and mode for each environment — Authentication and Test mode.

  3. Know what happened

    Get delivery, bounce and complaint events pushed to you — Webhooks.

  4. Make it production-safe

    Handle failures and retries — Errors, Rate limits and Idempotency.

API basics#

  • Base URL: https://api.poststack.dev. Request and response bodies are JSON.
  • Every request carries Authorization: Bearer <api key>.
  • Errors come back as { "error": "…" } with an HTTP status.
  • Lists page with page and per_page — Pagination.
bash
curl https://api.poststack.dev/domains \
  -H "Authorization: Bearer sk_live_…"

Getting started#

Introduction

What PostStack is, the base URL, and how these docs are organised.

Quickstart

From a new account to a delivered email in 10–20 minutes.

Authentication

API keys, their permissions and modes, and how to send them.

Errors

The error format and the status codes the API returns.

Rate limits

Request limits per endpoint, the 429 response, and sending quotas.

Pagination

page and per_page, the meta object, and walking every page.

Idempotency

Retry a send without delivering it twice.

Data regions

Where your data is stored and processed.

Test mode

Test keys that run the whole pipeline without delivering anything.

Sending#

Emails

Send, batch, schedule, cancel and look up transactional email.

Templates

Reusable subject and body with variables, filled in at send time.

Broadcasts

Campaigns to a segment, with scheduling and A/B tests.

Workflows

Automations that send email when something happens.

Tracking

Open and click tracking, and what the numbers mean.

SMTP relay

Send through smtp.poststack.dev from any SMTP client.

Receiving#

Inbound email

Receive mail on your domain and get it as JSON.

Mailboxes

Hosted mailboxes your team reads over IMAP or webmail.

Notification channels

Alerts in Slack, Discord or Telegram.

Audience#

Contacts

The people you send to, and their properties.

Contact properties

Custom fields on contacts.

Segments

Groups of contacts to send broadcasts to.

Subscription topics

Let contacts choose which kinds of mail they get.

Signup forms

Embeddable forms that add contacts.

Suppressions

Addresses PostStack will not send to, and why.

Configuration#

Domains

Add, verify and authenticate your sending domains.

Webhooks

Signed HTTP callbacks for email events.

Email validation

Check an address before you send to it.

Reference#

SDK reference

The TypeScript SDK, method by method.

MCP server

Let AI agents use PostStack through MCP tools.

Framework guides#

Copy-paste setup for your language or framework, over the SDK or SMTP: