feat: add Django email backend, supporting Django 4.2 LTS through 6.1

Add postmark.django.EmailBackend, a drop-in EMAIL_BACKEND gated behind a
new optional `django` extra (pip install postmark-python[django]):

- EmailBackend builds the Postmark payload from EmailMessage's high-level
  attributes (to/cc/bcc/subject/body/alternatives/attachments/extra_headers)
  rather than EmailMessage.message(), so it isn't affected by Django 6.0's
  modernized email API.
- PostmarkEmailMessage / PostmarkEmailMultiAlternatives / PostmarkEmailMixin
  for setting tag, metadata, and message_stream.
- pre_send / post_send / on_exception signals.
- Settings: POSTMARK_SERVER_TOKEN, POSTMARK_TEST_MODE, POSTMARK_TRACK_OPENS,
  POSTMARK_MESSAGE_STREAM.

Testing and CI:
- tests/django_backend/ (32 tests: sending, batching/chunking, attachments,
  headers, Unicode round-trip, fail_silently, signals, a regression test
  proving .message() is never called).
- New django-tests CI job matrixed across Django 4.2/5.2/6.0/6.1.
- tests/conftest.py now skips collecting tests/django_backend/ gracefully
  when the django extra isn't installed, instead of failing collection for
  the whole suite.

Docs and examples:
- examples/django/ (simple send, batch, attachment, custom header, external
  image, tags/metadata, settings snippet).
- README Django section with install/quickstart.

Also included: PyPI keywords, CONTRIBUTING.md, and GitHub issue templates
for discoverability and contribution ergonomics.

Author: gregsvo

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,28 @@
+---
+name: Bug report
+about: Report something that isn't working as expected
+title: ""
+labels: bug
+assignees: ""
+---
+
+**Describe the bug**
+A clear description of what's wrong.
+
+**To reproduce**
+Minimal code sample that reproduces the issue:
+
+```python
+
+```
+
+**Expected behavior**
+What you expected to happen instead.
+
+**Environment**
+- `postmark-python` version:
+- Python version:
+- OS:
+
+**Additional context**
+Anything else relevant (stack trace, `X-Request-Id` from an exception, etc.).

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Security vulnerability
+    url: https://github.com/ActiveCampaign/postmark-python/security/policy
+    about: Please report security vulnerabilities privately per SECURITY.md, not as a public issue.
+  - name: Postmark API / account support
+    url: mailto:support@postmarkapp.com
+    about: For questions about the Postmark service itself, rather than this SDK.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,19 @@
+---
+name: Feature request
+about: Suggest an addition or improvement to this SDK
+title: ""
+labels: enhancement
+assignees: ""
+---
+
+**What are you trying to do?**
+Describe the use case this would unlock.
+
+**Proposed solution**
+What you'd like the SDK to support, e.g. a new method, client, or option.
+
+**Alternatives considered**
+Any workarounds you're using today, or other approaches you considered.
+
+**Additional context**
+Links to relevant [Postmark API docs](https://postmarkapp.com/developer), if applicable.

.github/workflows/tests.yml

@@ -46,6 +46,42 @@ jobs:
         run: |
           poetry run pytest --cov=postmark --cov-report=xml --cov-report=term --cov-fail-under=85
 
+  django-tests:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        # Currently supported Django release series. The main `test` job above
+        # already exercises tests/django_backend/ against the pinned dev version
+        # (Django 5.2) across every supported Python version; this job additionally
+        # checks the Django backend against the rest of the support matrix.
+        django-version: ["4.2", "5.2", "6.0", "6.1"]
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Set up Python
+        uses: actions/setup-python@v7
+        with:
+          # 3.12 is the one Python version every entry in the matrix supports:
+          # Django 4.2 added 3.12 support in 4.2.8; Django 6.0/6.1 require 3.12+.
+          python-version: "3.12"
+
+      - name: Install Poetry
+        uses: snok/install-poetry@v1
+        with:
+          version: 2.4.1
+          virtualenvs-create: true
+          virtualenvs-in-project: true
+
+      - name: Install dependencies
+        run: poetry install --no-interaction
+
+      - name: Install Django ${{ matrix.django-version }}
+        run: poetry run pip install "django~=${{ matrix.django-version }}.0"
+
+      - name: Run Django backend tests
+        run: poetry run pytest tests/django_backend/ -v
+
   lint:
     runs-on: ubuntu-latest
 

CHANGELOG.md

@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ---
 
+## [Unreleased]
+
+### Added
+
+- Django email backend (`postmark.django.EmailBackend`), gated behind the new `django` extra (`pip install postmark-python[django]`). Supports Django 4.2 LTS, 5.2 LTS, 6.0, and 6.1 — including Django 6.0's ["modern email API" change](https://docs.djangoproject.com/en/6.0/releases/6.0/#adoption-of-python-s-modern-email-api). The Postmark payload is built from `EmailMessage`'s high-level attributes rather than `EmailMessage.message()`, so this backend is unaffected by that change.
+  - `postmark.django.PostmarkEmailMessage` / `PostmarkEmailMultiAlternatives` / `PostmarkEmailMixin` for setting `tag`, `metadata`, and `message_stream`.
+  - `postmark.django.pre_send` / `post_send` / `on_exception` signals.
+  - New settings: `POSTMARK_SERVER_TOKEN`, `POSTMARK_TEST_MODE`, `POSTMARK_TRACK_OPENS`, `POSTMARK_MESSAGE_STREAM`.
+  - See the [Django Backend wiki page](https://github.com/ActiveCampaign/postmark-python/wiki/Django-Backend) and `examples/django/`.
+
+---
+
 ## [0.3.7] - 2026-08-05
 
 ### Fixed

CONTRIBUTING.md

@@ -0,0 +1,41 @@
+# Contributing
+
+Thanks for considering a contribution to `postmark-python`.
+
+## Getting started
+
+```bash
+git clone https://github.com/ActiveCampaign/postmark-python.git
+cd postmark-python
+poetry install
+poetry run pre-commit install
+```
+
+## Making a change
+
+1. Fork the repository and create a feature branch off `main`.
+2. Make your change, keeping it scoped to a single concern.
+3. Add or update tests under `tests/` — the suite follows a one-file-per-feature layout (e.g. `test_templates.py`, `test_bounces.py`) that mirrors `postmark/models/`.
+4. Run the full check suite locally before opening a PR:
+
+   ```bash
+   poetry run pytest
+   poetry run ruff check
+   poetry run ruff format --check
+   poetry run mypy postmark/
+   poetry run pre-commit run --all-files
+   ```
+
+   CI enforces a minimum test coverage of 85% (`--cov-fail-under=85`), so new code needs tests to match.
+5. Update `CHANGELOG.md` under an `Unreleased` heading (Keep a Changelog format).
+6. Open a pull request describing the change and why it's needed.
+
+## Reporting bugs and requesting features
+
+Please open a [GitHub issue](https://github.com/ActiveCampaign/postmark-python/issues) using the appropriate template. For security vulnerabilities, follow the process in [SECURITY.md](SECURITY.md) instead of filing a public issue.
+
+## Code style
+
+- Formatting and linting are enforced by `ruff` (see `[tool.ruff]` in `pyproject.toml`).
+- Type hints are required; `mypy postmark/` must pass cleanly.
+- Request/response schemas use Pydantic v2 models under `postmark/models/<feature>/schemas.py`.

README.md

@@ -105,6 +105,22 @@ client = postmark.ServerClient(os.environ["POSTMARK_SERVER_TOKEN"])
 await client.close()
 ```
 
+## Django
+
+`postmark.django.EmailBackend` is a drop-in `EMAIL_BACKEND` for Django's `django.core.mail`, supporting Django 4.2 LTS through 6.1. Requires the `django` extra:
+
+```bash
+pip install postmark-python[django]
+```
+
+```python
+# settings.py
+EMAIL_BACKEND = "postmark.django.EmailBackend"
+POSTMARK_SERVER_TOKEN = "your-server-token"
+```
+
+See the [Django Backend wiki page](https://github.com/ActiveCampaign/postmark-python/wiki/Django-Backend) and [`examples/django/`](examples/django/) for tags, metadata, attachments, and signals.
+
 ## Development
 
 ```bash
@@ -124,11 +140,7 @@ poetry run pre-commit run --all-files
 
 ## Contributing
 
-1. Fork the repository
-2. Create a feature branch
-3. Add tests for your changes
-4. Ensure all checks pass (`poetry run pre-commit run --all-files`)
-5. Open a Pull Request
+See [CONTRIBUTING.md](CONTRIBUTING.md) for setup, testing, and PR guidelines.
 
 ## Support
 

examples/django/send_batch.py

@@ -0,0 +1,42 @@
+"""
+Send several distinct messages in one call. django.core.mail.send_mass_mail
+takes tuples of (subject, message, from_email, recipient_list) and sends them
+through a single connection — the Django backend batches them into Postmark's
+send_batch API (up to 500 per request) rather than one request per message.
+
+Run:
+    poetry run python examples/django/send_batch.py
+    python examples/django/send_batch.py  # with venv active
+"""
+
+import os
+
+import django
+from django.conf import settings
+
+try:
+    from dotenv import load_dotenv
+
+    load_dotenv()
+except ImportError:
+    pass
+
+if not settings.configured:
+    settings.configure(
+        EMAIL_BACKEND="postmark.django.EmailBackend",
+        POSTMARK_SERVER_TOKEN=os.environ["POSTMARK_SERVER_TOKEN"],
+    )
+    django.setup()
+
+from django.core.mail import send_mass_mail  # noqa: E402
+
+SENDER = os.environ["POSTMARK_SENDER_EMAIL"]
+
+sent_count = send_mass_mail(
+    (
+        ("Batch 1", "Hello Receiver 1", SENDER, ["receiver1@example.com"]),
+        ("Batch 2", "Hello Receiver 2", SENDER, ["receiver2@example.com"]),
+    )
+)
+
+print(f"Sent: {sent_count}")

examples/django/send_simple.py

@@ -0,0 +1,44 @@
+"""
+Send a single email through Postmark's Django backend.
+
+Standalone script, not a full Django project — real projects configure
+settings.py once (see settings_snippet.py) and just call
+django.core.mail.send_mail(...) anywhere.
+
+Run:
+    poetry run python examples/django/send_simple.py
+    python examples/django/send_simple.py  # with venv active
+"""
+
+import os
+
+import django
+from django.conf import settings
+
+try:
+    from dotenv import load_dotenv
+
+    load_dotenv()
+except ImportError:
+    pass
+
+if not settings.configured:
+    settings.configure(
+        EMAIL_BACKEND="postmark.django.EmailBackend",
+        POSTMARK_SERVER_TOKEN=os.environ["POSTMARK_SERVER_TOKEN"],
+    )
+    django.setup()
+
+from django.core.mail import send_mail  # noqa: E402
+
+SENDER = os.environ["POSTMARK_SENDER_EMAIL"]
+
+send_mail(
+    subject="Hello from Postmark",
+    message="Sent with postmark.django.EmailBackend.",
+    from_email=SENDER,
+    recipient_list=["receiver@example.com"],
+    html_message="<p>Sent with <b>postmark.django.EmailBackend</b>.</p>",
+)
+
+print("Sent.")

examples/django/send_simple_with_attachment.py

@@ -0,0 +1,49 @@
+"""
+Send an email with an attachment through Postmark's Django backend.
+
+Attachment content is base64-encoded automatically — pass the raw
+bytes/str you'd normally give EmailMessage.attach(), same as any other
+Django email backend.
+
+Run:
+    poetry run python examples/django/send_simple_with_attachment.py
+    python examples/django/send_simple_with_attachment.py  # with venv active
+"""
+
+import os
+
+import django
+from django.conf import settings
+
+try:
+    from dotenv import load_dotenv
+
+    load_dotenv()
+except ImportError:
+    pass
+
+if not settings.configured:
+    settings.configure(
+        EMAIL_BACKEND="postmark.django.EmailBackend",
+        POSTMARK_SERVER_TOKEN=os.environ["POSTMARK_SERVER_TOKEN"],
+    )
+    django.setup()
+
+from django.core.mail import EmailMessage  # noqa: E402
+
+SENDER = os.environ["POSTMARK_SENDER_EMAIL"]
+
+message = EmailMessage(
+    subject="Your report and resources",
+    body="Please find your report attached.",
+    from_email=SENDER,
+    to=["receiver@example.com"],
+)
+message.attach("report.txt", "Q3 sales are up 12%.", "text/plain")
+
+with open("/path/to/book.pdf", "rb") as f:
+    message.attach("book.pdf", f.read(), "application/pdf")
+
+message.send()
+
+print("Sent.")