Template Engine

MiniJinja Templating

EuroMail uses MiniJinja as its template engine, which provides Jinja2-compatible syntax familiar to developers who have worked with Python, Ansible, or static site generators. Templates are rendered server-side before SMTP delivery, so recipients receive fully composed HTML emails.

Variable Substitution

Use double curly braces to insert dynamic values into your templates:

<h1>Hello, {{ customer_name }}!</h1>
<p>Your order <strong>#{{ order_id }}</strong> has been confirmed.</p>

When sending an email, pass the variables in the API request body:

{
  "from": "[email protected]",
  "to": "[email protected]",
  "template_id": "order-confirmation",
  "variables": {
    "customer_name": "Anna",
    "order_id": "EM-20260309-4821"
  }
}

Conditionals, Loops, and Filters

MiniJinja supports control flow and data transformation within templates:

{% if shipping_method == "express" %}
  <p>Your order will arrive within 1-2 business days.</p>
{% else %}
  <p>Your order will arrive within 5-7 business days.</p>
{% endif %}

<h2>Order Items</h2>
<table>
  {% for item in items %}
  <tr>
    <td>{{ item.name }}</td>
    <td>{{ item.quantity }}</td>
    <td>{{ item.price | round(2) }} EUR</td>
  </tr>
  {% endfor %}
</table>

<p>Total: {{ total | round(2) }} EUR</p>

Filters like round, upper, lower, length, and default are available for transforming values inline.

Managing Templates via API

Templates can be created, updated, and versioned through the REST API:

curl -X POST https://api.euromail.dev/v1/templates \
  -H "X-EuroMail-Api-Key: em_live_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "order-confirmation",
    "subject": "Order #{{ order_id }} Confirmed",
    "html_body": "<h1>Thanks, {{ customer_name }}!</h1>..."
  }'

You can also manage templates through the dashboard, which provides a visual editor with live preview.

Template Versioning

Every update to a template creates a new version. Previous versions are retained, allowing you to roll back if needed. The API returns the current version number with each template response.

Server-Side Rendering

Templates are rendered by the EuroMail worker process immediately before SMTP delivery. This means the recipient's mail client receives a fully rendered HTML email with no template syntax visible. If a required variable is missing, the email is rejected with a clear error message rather than sent with broken placeholders.