edx-platform/common/djangoapps/student/templates/unsubscribed_emails/email/body.html

{% extends "unsubscribed_emails/email/base.html" %}
{% block body %}

<p>
    Please find attached CSV file for Unsubscribed Emails from <strong>{{ start_date }}</strong> to <strong>{{ end_date }}</strong>
</p>

{% endblock body %}