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Postmark

Postmark API

Yes. Postmark publishes a public REST API. See developer.postmarkapp.com for pricing details.

MCP also available
Open API docsTry Postmark
Public REST API documentedAgent-readiness 7/10
Data from Buddy's database, auto-rechecked weekly

What is the Postmark API?

The Postmark API is a public REST interface to campaigns, contacts, segments, and automation workflows. Auth method is documented on the official API reference. No official SDK was detected, so most teams hit it directly with HTTP clients.

Typical builds: scripts that sync subscribers from your product database, engagement dashboards that combine open rate with revenue attribution, and cron jobs that pause underperforming campaigns automatically.

For agent workflows specifically, the official MCP server is usually less code than the REST API. The API still wins for scheduled jobs, dashboards, and anything outside an LLM-driven flow.

For the broader picture: Postmark review, full pricing breakdown, .

HOOK IT TO YOUR STACK

Real Postmark API calls you'll write

postmark-apirest
#List campaigns from the last 30 days
GET/v3/campaigns?since=30d&fields=name,open_rate,clicks
200 OK · 12 campaigns
Black Friday Teaseropen 42.1%
Product launchopen 38.5%
Weekly digest #12open 27.0%
Welcome flow step 2open 61.3%
postmark-apirest
#Create a new automation programmatically
POST/v3/automations
201 Created · automation_id: aut_8x
Statusdraft
Steps configured0
Estimated audience2,847
Push steps via PUT /automations/{id}/steps.
postmark-apirest
#Add a contact and tag them in one call
POST/v3/contacts
201 Created · contact_id: c_4f12
Lifecycle stagesubscriber
Tags applied1
Triggers firedwelcome-series
TMB SCORE FOR PostmarkAgent fit: 7/10
Read review →

Endpoints illustrative. Confirm exact paths against the live API docs before integrating.

How much does the Postmark API actually cost?

Verify on docs

Postmark publishes an API, but per-tier gating wasn't extracted automatically.

  • Most likely scenario: API access is either included in all paid plans, or it's gated to higher tiers and we need to verify on the live docs page.
  • Until verified, treat the question "which plan unlocks the API" as open. Don't budget on the assumption it's free with the cheapest paid plan.

API at a glance

Auth method
—
SDK languages
—
OpenAPI spec
—
Webhooks
—
Structured outputs
—

Postmark also has an MCP server

If you're wiring Postmark into Claude / Cursor / Codex, the MCP server is usually less code than the REST API.

See Postmark MCP page

What you can build with the Postmark API

Three personas, three different shapes of build. Pick the row that matches how you actually ship.

SOLO DEV / FOUNDER

Glue Postmark into your daily workflow

  • Pull a digest of campaign performance into your morning Slack
  • Trigger a one-off backfill when something looks off
  • Pipe data into your own SQLite for ad-hoc queries
Effort: A weekend, one Node or Python script
AGENCY / CONSULTANT

Sell Postmark reporting at scale

  • White-label Postmark data into client-branded dashboards
  • Run scheduled multi-account reports without logging into the Postmark UI
  • Cross-reference with the rest of the client's stack (CRM, analytics, ad spend)
Effort: 1-2 weeks, hits multi-tenant auth quickly
IN-HOUSE ENGINEER

Production pipelines for Postmark

  • Real-time sync into your warehouse on a cron
  • Custom alerts the dashboard's built-in alerting can't express
  • Backfill + idempotency handling for Postmark data older than the dashboard exposes
Effort: Multi-week project, expect rate-limit tuning

Quickstart template

# Starter template — endpoint paths and SDK package names come from
# the Postmark API docs: https://developer.postmarkapp.com

curl -X GET "https://developer.postmarkapp.com/<your-endpoint>" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Accept: application/json" | jq .

Template only. Endpoint paths, exact base URL, and auth header format come from developer.postmarkapp.com.

Limits and gotchas

  • No OpenAPI spec — you write typed clients by hand or use a third-party generator on the docs HTML.
  • No official SDK detected. Plan on hitting the API directly with your HTTP client of choice.
  • Rate limits: always read the docs page before scaling — the published limit is usually lower than the practical one and overages can be expensive.
7/10

Agent-readiness verdict

Moderate agent-fit with official MCP support. Postmark offers an official MCP server and documented public API, giving agents direct access to transactional email workflows. The lack of OpenAPI specs, SDKs, and webhook support limits deeper integrations and real-time event handling.

MCP server availableOfficial MCP (on tool's own domain)Public API with docs

Postmark API FAQ

Does Postmark have a public API?+
Yes — REST API at developer.postmarkapp.com.
Should I use the API or the MCP server for Claude / Cursor / Codex?+
Prefer the MCP server for agent workflows — it's less code and pre-handles auth flows. Use the REST API for scheduled jobs, dashboards, and anything outside an LLM-driven flow.

Sources

Joonas Rotko
Joonas RotkoAuthor & Founder of That Marketing Buddy

10+ years in digital marketing. I review marketing software for AI-stack fit: real pricing, MCP and API support, and how cleanly each tool drops into an AI agent workflow, cross-checked against verified data and real user feedback.

About meHow I review

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