php - Symfony mailer raw content is weird, contains =20 =3D =

And this is my code:

$email = (new TemplatedEmail())
            ->from(new Address($this->container->getParameter('mailer_no_replay'), 'B2B Marketing'))//TODO: Translation
            ->to(new Address($lead->getEmail(), $lead->getName()))
            ->subject($emailTemplate->getSubject())
            ->htmlTemplate('emails/email-messages/crm-email.html.twig')
            ->context([
                'user' => $lead,
                'content' => $mailContent,
            ]);
        $this->mailer->send($email);

And the templates:

1: child (extends 2)

{% extends 'emails/content-email.html.twig' %}
{% block emailMessage %}
    {{ content | raw}}
{% endblock %}

2: parent

{% extends 'emails/emailBase.html.twig' %}
{#
This Template used for rendering emails that just have a content not need to render anything else
#}
{% block content %}
    <div style="background-color:#ffffff;">
        <div class="block-grid"
             style="Margin: 0 auto; min-width: 320px; max-width: 790px; overflow-wrap: break-word; word-wrap: break-word; word-break: break-word; background-color: #e8f5f8;">
            <div style="border-collapse: collapse;display: table;width: 100%;background-color:#e8f5f8;">
                <!--[if (mso)|(IE)]>
                <table width="100%" cellpadding="0" cellspacing="0" border="0"
                       style="background-color:#ffffff;">
                    <tr>
                        <td align="center">
                            <table cellpadding="0" cellspacing="0" border="0" style="width:790px">
                                <tr class="layout-full-width" style="background-color:#e8f5f8"><![endif]-->
                <!--[if (mso)|(IE)]>
                <td align="center" width="790"
                    style="background-color:#e8f5f8;width:790px; border-top: 0px solid transparent; border-left: 0px solid transparent; border-bottom: 0px solid transparent; border-right: 0px solid transparent;"
                    valign="top">
                    <table width="100%" cellpadding="0" cellspacing="0" border="0">
                        <tr>
                            <td style="padding-right: 25px; padding-left: 25px; padding-top:60px; padding-bottom:60px;">
                <![endif]-->
                <div class="col num12"
                     style="min-width: 320px; max-width: 790px; display: table-cell; vertical-align: top; width: 790px;">
                    <div style="width:100% !important;">
                        <!--[if (!mso)&(!IE)]><!-->
                        <div
                            style="border-top:0px solid transparent; border-left:0px solid transparent; border-bottom:0px solid transparent; border-right:0px solid transparent; padding-top:60px; padding-bottom:60px; padding-right: 25px; padding-left: 25px;">
                            <!--<![endif]-->
                            <!--[if mso]>
                            <table width="100%" cellpadding="0" cellspacing="0" border="0">
                                <tr>
                                    <td style="padding-right: 20px; padding-left: 20px; padding-top: 10px; padding-bottom: 5px; font-family: Arial, sans-serif">
                            <![endif]-->
                            <div
                                style="color:#34495e;font-family:Open Sans, Helvetica Neue, Helvetica, Arial, sans-serif;line-height:1.5;padding-right:20px;padding-bottom:5px;padding-left:20px;">
                                <div
                                    style="line-height: 1.5; font-size: 13px; color: #34495e; font-family: Open Sans, Helvetica Neue, Helvetica, Arial, sans-serif; mso-line-height-alt: 18px;">
                                    {% block emailMessage %}{% endblock %}
                                </div>
                            </div>
                        </div>
                        <!--<![endif]-->
                    </div>
                </div>
                <!--[if (mso)|(IE)]></td></tr></table><![endif]-->
                <!--[if (mso)|(IE)]></td></tr></table></td></tr></table><![endif]-->
            </div>
        </div>
    </div>
{% endblock %}

Solution:

These characters are:

Quoted-Printable, or QP encoding, is a binary-to-text encoding system using printable ASCII characters. QP works by using the equals sign = as an escape character.

Example: The following example is a French text (encoded in UTF-8), with a high frequency of letters with diacritical marks (such as the ?�).

J'interdis aux marchands de vanter trop leurs marchandises. Car ils se font=
vite p=C3=A9dagogues et t'enseignent comme but ce qui n'est par essence qu=
'un moyen, et te trompant ainsi sur la route =C3=A0 suivre les voil=C3=
=A0 bient=C3=B4t qui te d=C3=A9gradent, car si leur musique est vulgaire il=
s te fabriquent pour te la vendre une =C3=A2me vulgaire.
   =E2=80=94=E2=80=89Antoine de Saint-Exup=C3=A9ry, Citadelle (1948)

This encodes the following quotation:

J'interdis aux marchands de vanter trop leurs marchandises. Car ils se font vite p?�dagogues et t'enseignent comme but ce qui n'est par essence qu'un moyen, et te trompant ainsi sur la route ?� suivre les voil?� bient??t qui te d?�gradent, car si leur musique est vulgaire ils te fabriquent pour te la vendre une ??me vulgaire.

??�??�Antoine de Saint-Exup?�ry, Citadelle (1948)