email – Windows 10 Mail App Mangled Sent Message

I sent an email from the Windows 10 Mail app and it looks like the encoding got messed up. I was wondering if anyone knows what I did wrong and how to avoid this in the future? I’ve included Gmail’s original copy below, with the personal info removed. This is what it looks like in the web browser when I view the sent message, the recipient would see HTML code instead of the formatted message. I’m thinking that there’s a " character that Mail autofilled and messed everything up?

Return-Path: <>
Received: from ((
        by with ESMTPSA id example
        for <>
        (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128);
        Wed, 11 Nov 2020 17:03:10 -0800 (PST)
MIME-Version: 1.0
Date: Wed, 11 Nov 2020 20:03:06 -0500
From: John <>
Subject: Example
Thread-Topic: Example
Message-ID: <example>
To: "

" <>
Content-Transfer-Encoding: quoted-printable
Content-Type: text/html; charset="utf-8"

<html xmlns:o=3D"urn:schemas-microsoft-com:office:office" xmlns:w=3D"urn:sc=
hemas-microsoft-com:office:word" xmlns:m=3D"
fice/2004/12/omml" xmlns=3D""><head><meta ht=
tp-equiv=3DContent-Type content=3D"text/html; charset=3Dutf-8"><meta name=
=3DGenerator content=3D"Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
    {font-family:"Cambria Math";
    panose-1:2 4 5 3 5 4 6 3 2 4;}
    panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
a:link, span.MsoHyperlink
@page WordSection1
    {size:8.5in 11.0in;
    margin:1.0in 1.0in 1.0in 1.0in;}
--></style></head><body lang=3DEN-US link=3D"#0563C1" vlink=3D"#954F72"><di=
v class=3DWordSection1><p class=3DMsoNormal>Some text some text some text s=

. . .