base.mjml

<mjml>
  <mj-head>
    <mj-attributes>
      <mj-all font-family="Helvetica"></mj-all>
    </mj-attributes>
  </mj-head>
  <mj-body background-color="#f6f6f6">
    <mj-raw>
      {% trans_default_domain 'email' %}
      <!-- Company Header -->
    </mj-raw>
    <mj-section background-color="#a9a9a9" padding-top="10px" padding-bottom="10px">
      <mj-column>
        <mj-text font-size="20px" color="#ffffff">
          {{ 'base.header_text'|trans }}
        </mj-text>
      </mj-column>
    </mj-section>
    <mj-raw>{% block email_body %}</mj-raw>
    <mj-raw>
      <!-- Main body -->
    </mj-raw>
    <mj-section background-color="#ffffff" padding="20px">
      <mj-column>
        <mj-text>
          <h1>{{ email_body_title|trans }}</h1> {{ email_body_text|trans|raw }}</mj-text>
        <mj-raw>
          <tr>
            <td style="word-wrap:break-word;font-size:0px;padding:10px 25px;" align="left">
              <div>
                <!--[if mso]>
                <v:rect xmlns:v="urn:schemas-microsoft-com:vml" xmlns:w="urn:schemas-microsoft-com:office:word" href="{{ button_url }}" style="height:55px;v-text-anchor:middle;width:226px;" stroke="f" fillcolor="#90bf48">
                  <w:anchorlock/>
                  <center>
                <![endif]--><a href="{{ button_url }}" style="background-color:#a9a9a9;color:#ffffff;display:inline-block;font-family:'Helvetica';font-size:13px;font-weight:bold;line-height:55px;text-align:center;text-decoration:none;width:226px;-webkit-text-size-adjust:none;text-transform:uppercase;">{{ button_text|trans }}</a>
                <!--[if mso]>
                  </center>
                </v:rect>
                <![endif]-->
              </div>
            </td>
          </tr>
        </mj-raw>
        <mj-text padding="0 25px 10px">{{ email_body_bottom_text|trans|raw }}</mj-text>
        <mj-text>
            {{ 'base.ending_closing'|trans }},<br />
            {{ 'base.ending_signature'|trans }}
        </mj-text>
      </mj-column>
    </mj-section>
    <mj-raw>{% endblock email_body %}</mj-raw>
    <mj-wrapper padding-top="0">
      <mj-section full-width="full-width" background-color="#f6f6f6" padding-top="0" padding-bottom="0px">
        <mj-column>
          <mj-text align="center" font-family="Helvetica">{{ 'base.header_text'|trans }}</mj-text>
        </mj-column>
      </mj-section>
    </mj-wrapper>
  </mj-body>
</mjml>

passwordReset.html.twig

{% extends 'email/base.html.twig' %}

{% set email_body_title = 'password_reset.body_title' %}
{% set button_url = absolute_canonical_url(path('password_reset_token', {token: user.passwordResetToken})) %}
{% set button_text = 'password_reset.button_text' %}
{% set email_body_text = 'password_reset.body_text' %}
{% set email_body_bottom_text = 'password_reset.body_bottom_text' %}

{% block email_body %}
  {{ parent() }}
{% endblock email_body %}

{% block app_info_box %}
{% endblock app_info_box %}