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django-letter

Write an email once as a Django template. Send it as HTML with inlined CSS and a plain-text alternative.

django-letter renders your markup, inlines the CSS, and derives a Gmail-style plain-text body from the same template.

Setup

1. Add the package:

   uv add django-letter
   

2. Add the app to your settings:

   # settings.py
   INSTALLED_APPS = [
       "django_letter",
       # ...
   ]
   

3. Add an emails.py module to each app that sends mail. Put it next to that app's views.py.

4. Mount the debug pages in your root URLconf:

   # urls.py
   from django.urls import include, path
   
   urlpatterns = [
       path("emails/", include("django_letter.urls")),
   ]
   

   While DEBUG is true, you can preview each email at /emails/:

   

Usage

Make a pretty email

Subclass TemplateEmail. Set template_name, subject, and the values your markup needs. This example attaches the invoice and adds a tracking button:

# myapp/emails.py
from django.utils.translation import gettext_lazy as _

from django_letter import TemplateEmail


class OrderShippedEmail(TemplateEmail):
    template_name = "emails/order_shipped.html"
    subject = _("Order %(number)s has shipped")
    preheader = _("Track your parcel with the link inside.")

    def __init__(self, order, **kwargs):
        self.order = order
        super().__init__(**kwargs)

    def get_context_data(self):
        return {"order": self.order, "number": self.order.number}

    def gen_attachments(self):
        yield "invoice.pdf", self.order.invoice, "application/pdf"

subject and preheader fill their %(name)s placeholders from the context of the template. Write %% for a literal percent sign. gen_attachments() yields (filename, content, MIME type) tuples. Use None as the MIME type and Python guesses it from the file name.

The template extends the bundled base template and fills the content block:

{# myapp/templates/emails/order_shipped.html #}
{% extends "django_letter/base.html" %}
{% load django_letter %}

{% block content %}
  <h1>Thanks for your order</h1>
  <p>Order {{ number }} is on its way.</p>
  {% button href=order.tracking_url value="Track parcel" primary=True %}
  {% table class="summary" %}
    <tr>
      <td>Invoice</td>
      <td>{{ number }}</td>
    </tr>
  {% endtable %}
{% endblock content %}

{% button %} builds a table that Outlook keeps intact, with the link in a new tab. primary uses the accent color of the base template. disabled shows the label as plain text without a link.

{% table %} wraps the rows in a layout table that every email client understands. Each keyword argument becomes an attribute. The tag adds role="presentation", border="0", cellpadding="0" and cellspacing="0", and it escapes each attribute value.

The base template keeps the layout safe for email clients and inlines the CSS when the message is built. It writes subject into <title> and preheader into a hidden span. Its blocks are container, logo, content, footer and footer_content. Its classes cover the layout (container, content, main, wrapper, footer, content-block), alignment (align-left, align-right, align-center) and spacing (first, last, mt0, mb0).

Add your own <style> rules in the extra_header block. The package inlines them:

{% block extra_header %}
  <style>
    .brand {
      color: #bada55;
    }
  </style>
{% endblock extra_header %}

OrderShippedEmail(order, to=["customer@example.com"], language="de").send()
OrderShippedEmail.to_user(user, order=order, language="de").send()

Test it

Render the email in your tests without a mail backend:

def test_order_shipped():
    email = OrderShippedEmail.render_preview(order=order)

    assert "Order A-1 is on its way" in email.html
    assert "Track parcel <https://example.com/track/A-1>" in email.body

render_preview() returns the rendered email. It takes the constructor arguments of the class. context= merges extra values over get_context_data(). language= picks the language. The email carries html, body, subject and attachments.

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