Documentation

Overview

mailstein is a transactional and broadcast email platform that sends from infrastructure you control. Everything the dashboard does is available over a REST API, SMTP, and official libraries.

Base URL

Base URL https://app.mailstein.com/api/v1

Every request is JSON over HTTPS. The interactive reference with full request/response schemas lives at /api/v1/ui, and the raw OpenAPI 3.0 spec at /api/v1/doc.

Authentication

Authenticate with an API key created in the dashboard under Developers → API Keys. Keys start with ms_. Pass it as a bearer token on every request:

curl
curl https://app.mailstein.com/api/v1/domains \
  -H "Authorization: Bearer ms_your_api_key"
Treat the key like a password. It carries the permissions you granted it and is shown only once at creation — regenerate it from the dashboard if it leaks.

Send your first email

curl
curl -X POST https://app.mailstein.com/api/v1/emails \
  -H "Authorization: Bearer ms_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "you@yourdomain.com",
    "to": "someone@example.com",
    "subject": "Hello from mailstein",
    "html": "<p>It works.</p>"
  }'

Returns { "emailId": "em_..." }. See the Quickstart for the full path including domain verification.

Resources

Emails

Send, batch, schedule, cancel, and look up delivery status.

Domains

Add sending domains and verify SPF, DKIM and return-path.

Contacts

Contact books, contacts, bulk import and subscription state.

Campaigns

Create broadcasts, schedule, pause and resume sends.

Analytics

Email time-series and sending reputation metrics.

Webhooks

Real-time delivery, bounce, open and click events.

Three ways to send

Next →
Quickstart