Postmark

Warnings

• gotcha postmarker is a community library, not an official Postmark SDK. Postmark has no official Python SDK. postmarker is the recommended community option per Postmark's developer docs, but it is not maintained by Postmark.
  Fix: For actively maintained alternatives, use django-anymail[postmark] for Django projects, or make direct HTTP calls using requests to the Postmark REST API.
• gotcha postmarker v1.0 has no releases to PyPI in 12+ months as of mid-2025. The project may be effectively abandoned. Python 3.11+ compatibility has not been verified in recent releases.
  Fix: Test compatibility with your Python version before relying on postmarker in production. Consider django-anymail as a more actively maintained alternative.
• gotcha Field names in postmarker follow Postmark's PascalCase API convention, not Python snake_case. Code passing lowercase fields (from_email, html_body) is silently ignored or raises AttributeError.
  Fix: Use From=, To=, HtmlBody=, TextBody=, Subject= (PascalCase) as per Postmark API docs.
• gotcha PostmarkClient constructor kwarg is server_token=, not token=. An earlier version used token= — code from older tutorials passes token= and raises TypeError.
  Fix: PostmarkClient(server_token='YOUR_TOKEN')
• gotcha Use 'POSTMARK_API_TEST' as the server_token to send emails to Postmark's blackhole test environment (test@blackhole.postmarkapp.com). These emails are never delivered. Switch to a real server token for production.
  Fix: PostmarkClient(server_token='POSTMARK_API_TEST') for testing, PostmarkClient(server_token=os.environ['POSTMARK_SERVER_TOKEN']) for production.

Install

• pip install postmarker Python (community library, not official)
• pip install django-anymail[postmark] Django (recommended alternative — Anymail is actively maintained)

Imports

• PostmarkClient

  from postmarker.core import PostmarkClient
  
  postmark = PostmarkClient(server_token='SERVER_TOKEN')

  The kwarg is server_token, not token. Was renamed from 'token' in an earlier version — old tutorials using token= raise TypeError.
• Django backend

  # settings.py
  EMAIL_BACKEND = 'postmarker.django.EmailBackend'
  POSTMARK = {
      'TOKEN': 'SERVER_TOKEN',
      'TEST_MODE': False,
      'VERBOSITY': 0,
  }

  postmarker ships a Django email backend. Configure via POSTMARK dict in settings, not SMTP settings.

Quickstart

Field names match Postmark API exactly (PascalCase, not snake_case). Use 'POSTMARK_API_TEST' as token to send to the test/blackhole sandbox.

import os
from postmarker.core import PostmarkClient

postmark = PostmarkClient(server_token=os.environ['POSTMARK_SERVER_TOKEN'])

# Send single email
response = postmark.emails.send(
    From='sender@example.com',
    To='recipient@example.com',
    Subject='Hello from Postmark',
    HtmlBody='<strong>Hello!</strong>'
)
print(response['MessageID'])

# Send batch
postmark.emails.send_batch(
    {
        'From': 'sender@example.com',
        'To': 'recipient1@example.com',
        'Subject': 'Batch 1',
        'TextBody': 'Hello 1'
    },
    {
        'From': 'sender@example.com',
        'To': 'recipient2@example.com',
        'Subject': 'Batch 2',
        'TextBody': 'Hello 2'
    }
)

# Test token for sandbox
# postmark = PostmarkClient(server_token='POSTMARK_API_TEST')