The Stack · Email, SMS & voice comms API

Postmark

Fast, reliable transactional email API and SMTP known for deliverability and long message history.

API keyFree tier🔵 agent: self serve instant key

Get API key → instant key, usually no card Docs Website

CategoryEmail, SMS & voice comms

TypeAPI service

Authapi-key

PricingFree tier

Agent signup🔵 self serve instant key

SDKsNode, Python, Ruby, PHP, .NET, Go, Java, REST, SMTP

Pricing: Free dev plan: 100 emails/mo (never expires); paid from $15/mo for 10k emails

🔵 Agents: self serve instant key

Instant self-serve — free signup gives a key immediately (a human unblocks an agent in under 2 minutes).

Self-serve signup issues per-server API tokens immediately; sending accounts go through an approval check and sender-signature/domain verification before high-volume sending.

Postmark — Fast, reliable transactional email API and SMTP known for deliverability and long message history.
Website: https://postmarkapp.com
Docs: https://postmarkapp.com/developer
Get a key: https://account.postmarkapp.com/sign_up
Agent signup: self serve instant key — Self-serve signup issues per-server API tokens immediately; sending accounts go through an approval check and sender-signature/domain verification before high-volume sending.
Auth: api-key
Pricing: free-tier — Free dev plan: 100 emails/mo (never expires); paid from $15/mo for 10k emails
Full record: https://dreaming.press/api/tools/postmark.json

Machine record: /api/tools/postmark.json

Quickstart

import { ServerClient } from "postmark";

const client = new ServerClient("POSTMARK_SERVER_TOKEN");

await client.sendEmail({
  From: "you@yourdomain.com",
  To: "user@example.com",
  Subject: "Hello",
  HtmlBody: "<p>Sent with Postmark</p>",
});

javascript · full docs →

Postmark in our coverage

MCP Tool Poisoning: How a Poisoned Tool Description Turns Your Agent Against You

2026-07-04

Postmark FAQ

What is Postmark?

Postmark is Fast, reliable transactional email API and SMTP known for deliverability and long message history. It's in the Email, SMS & voice comms category of the dreaming.press tool directory.

Is Postmark free?

Postmark is free to start with a free tier. Free dev plan: 100 emails/mo (never expires); paid from $15/mo for 10k emails.

Can an AI agent sign up for Postmark automatically?

Almost — signup is instant and self-serve (a free key with no sales call), so a human can unblock an agent in under two minutes. Self-serve signup issues per-server API tokens immediately; sending accounts go through an approval check and sender-signature/domain verification before high-volume sending..

Does Postmark have an MCP server?

Postmark does not publish an official MCP server as of our last check.

Is Postmark open source?

Postmark is a hosted API service, not an open-source project.

What languages does Postmark support?

Postmark offers Node, Python, Ruby, PHP, .NET, Go, Java, REST, SMTP.

Postmark

Quickstart

Postmark in our coverage

MCP Tool Poisoning: How a Poisoned Tool Description Turns Your Agent Against You

Postmark FAQ

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