Breaking DKIM Alignment - ZOHO, HOW ABOUT A RESPONSE?!?!

I've emailed Zoho about this crucial issue and haven't received a response. If we can't get our Zoho email to pass DMARC alignment because Zoho is breaking DKIM by modifying our emails, and if Zoho Support won't respond in a timely manner, we'll take our paid email plan elsewhere.

So, for a third time:

-----------------------------------------------------------

I'm not getting DKIM alignment because of an error (signature did not verify) and a warning (l= tag included).

Upon further testing, I can see what is happening. I sent test emails using Postbox and Outlook email clients, as well as from Zoho.com. I have found that Zoho.com and Outlook submitted emails both produce the above errors, while email sent using Postbox software yields full alignment (aside from the warning of the l= tag).

Looking at the source code for all emails, I can see that Zoho and Outlook both break DKIM. Zoho.com and Outlook modify the headers in transit - either changing the Content-Type or adding HTML, or both. Note, these are both emails sent from @MyDomain.com to a single recipient email (no forwarder/alias address).

This email sent from Zoho.com (also note broken quotations ["]:

DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1572288084; s=zoho; d=MyDomain.com; i=me@MyDomain.com; h=Date:From:To:Message-Id:Subject:MIME-Version:Content-Type; l=620; bh=OeBT59YcrAZlNfvyrNpNHTYNlwfijzx1kaCbNGRwns4=; b=D3Vo8zs746N44c9tFwtaHpkhztB9a75OyzqKIdTVsnRQ8C2HlJtKXFD0wnjPfvvK UdRZMFq0+E3XbG55B9nmLWtGa36UbGII+VSNKxCxcKZrqXobWu0sBumGMhqMcHpOEEJ qoRI+GHt6LxlRUErxNPquNZ8x34DWHtXJCkqgdDM=

Received: from mail.zoho.com by mx.zohomail.com with SMTP id 1572288077891884.3493464741894; Mon, 28 Oct 2019 11:41:17 -0700 (PDT)
Date: Mon, 28 Oct 2019 11:41:17 -0700
From: MyDomain me <me@MyDomain.com>
To: personalemail <personalemail@gmail.com>
Message-Id: <16e13ac2042.cd44a040452320.2901939123071754741@MyDomain.com>
Subject: SL Zoho to Gmail
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="----=_Part_1442111_619895866.1572288077890"
X-Priority: Medium
User-Agent: Zoho Mail
X-Mailer: Zoho Mail

------=_Part_1442111_619895866.1572288077890
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit

Testing this out once again...

------=_Part_1442111_619895866.1572288077890
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: 7bit

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta content="text/html;charset=UTF-8" http-equiv="Content-Type"></head><body ><div style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt;">Testing this out once again...</div><br></body></html>
------=_Part_1442111_619895866.1572288077890--

This email sent via Outlook:

DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1572285895; s=zoho; d=MyDomain.com; i=business@MyDomain.com; h=From:To:References:In-Reply-To:Subject:Date:Message-ID:MIME-Version:Content-Type; l=2911; bh=55oF+Vtr7xAyCI+9fEOOLbGjyfa0E52iy36tJ5PPlFg=; b=Wdn3LaXGjO+zhoTR2EGR6DTJX+LVldSDEmWTdTm4gIQH3tLIzyTVwLe89UfbnfHF c5FFA6RUBPi+kxJd5qWA/Ek51MBizguuIO1rxckZfNT31UDp0tipm1LZj32J5MEvUpV i2YndTwcRMGokvyfNckz/J0WNBxXen0nDbV2W/X4=
Received: from MyPC (22.222.22.22 [22.222.22.22]) by mx.zohomail.com with SMTPS id 1572285893509749.9206635065016; Mon, 28 Oct 2019 11:04:53 -0700
From: <business@MyDomain.com>
To: <personalemail@gmail.com>
Subject: SL Outlook to Gmail
Date: Mon, 28 Oct 2019 14:04:51 -0400
Message-ID: <009001d58dba$3290edd0$97b2c970$@MyDomain.com>
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="----=_NextPart_000_0091_01D58D98.AB7F9BF0"
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AQMrjcYI76YKJTL13jlnlC+Yh/R+xaTEWLRw
Content-Language: en-us
X-ZohoMailClient: External

------=_NextPart_000_0091_01D58D98.AB7F9BF0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit

From: business@MyDomain.com <business@MyDomain.com>
Sent: Monday, October 28, 2019 2:01 PM
To: 'personalemail@gmail.com' <personalemail@gmail.com>
Subject: SL Outlook to Gmail

Testing testing testing

------=_NextPart_000_0091_01D58D98.AB7F9BF0
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: quoted-printable

<html xmlns:v=3D"urn:schemas-microsoft-com:vml" xmlns:o=3D"urn:schemas-micr=
osoft-com:office:office" xmlns:w=3D"urn:schemas-microsoft-com:office:word" =
xmlns:m=3D"http://schemas.microsoft.com/office/2004/12/omml" xmlns=3D"http:=
//www.w3.org/TR/REC-html40"><head><meta http-equiv=3DContent-Type content=
=3D"text/html; charset=3Dutf-8"><meta name=3DGenerator content=3D"Microsoft=
Word 15 (filtered medium)"><style></style></head><body lang=3DEN-US link=3D"#0563C1=
" vlink=3D"#954F72"><div class=3DWordSection1><p class=3DMsoNormal><b>From:=
</b> business@MyDomain.com <business@MyDomain.com> <br><b>Sent:=
</b> Monday, October 28, 2019 2:01 PM<br><b>To:</b> 'personalemail@gmail.com' =
<personalemail@gmail.com><br><b>Subject:</b> SL Outlook to Gmail<o:p></o=
:p></p><p class=3DMsoNormal><o:p> </o:p></p><p class=3DMsoNormal>Testi=
ng testing testing<o:p></o:p></p></div></body></html>
------=_NextPart_000_0091_01D58D98.AB7F9BF0--

and fully aligned email sent from Postbox:

DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1572282880; s=zoho; d=MyDomain.com; i=me@MyDomain.com; h=To:From:Message-ID:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding; l=2528; bh=wh6E9+UkredgM9cAiQ5v/ylrQjZi6SIluliT5hWHoW0=; b=PelPzzFJ1kKV9hX+QaZ1cJVBLXsbVA2gJSrxT9oudwMW2WNUUQmL427aNhDHZ1vJ J13mdMYJ+SAAQDulrXz3aNYqCMEV+M/orRBNMYADG97CKUusMjItveOf3aC1eZ+s5uD +lgUrOxIXfTP2BTPj2MxXeSJXtyBbIkzUKWhgU6Y=
Received: from [111.111.1.11] (22.222.22.22 [22.222.22.22]) by mx.zohomail.com with SMTPS id 1572282879750898.4677175428585; Mon, 28 Oct 2019 10:14:39 -0700 (PDT)
To: Me <personalemail@gmail.com>
From: MyDomain <me@MyDomain.com>
Message-ID: <5f9a1cda-5773-50ec-be96-e00c344e876e@MyDomain.com>
Subject: SL Postbox to Gmail
Date: Mon, 28 Oct 2019 13:14:37 -0400
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 PostboxApp/7.0.7
MIME-Version: 1.0
Content-Type: text/html; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: quoted-printable

<html theme=3D"tangaroa"><head>
<meta http-equiv=3D"content-type" content=3D"text/html; charset=3Dutf-8"></=
head><body
style=3D"font-family: Tahoma; font-size: 14px;" text=3D"#000000">
<div style=3D"font-size: 14px;font-family: Tahoma;">Testing once again<br><=
div
class=3D"moz-signature"><br>
=09
=09=09
<title></title>

=09
=09
=09=09
<hr style=3D"text-align:left;margin-left:0;width:400px;height:=20
12px;border: 0;box-shadow: inset 0 12px 12px -12px rgba(48, 51, 113,=20
1);">
=09=09
<div style=3D"height:10px;">
=09=09=09=C2=A0</div>

=09=09
<div>
=09=09=09<img=20
src=3D"http://www.MyDomain.com/v/vspfiles/images/Logos/MyDomainSig.p=
ng"><br>
=09=09=09<span style=3D"font-family:lucida sans unicode,lucida=20
grande,sans-serif;"><span style=3D"font-size: 14px; font-weight: bold;"><em=
>Tara</em>
| </span><span style=3D"color:#696969;"><span style=3D"font-size: 14px;">S=
tarlinks
Gifts</span></span></span>
=09=09=09<div style=3D"padding-top: 3px;">
=09=09=09=09<span style=3D"font-size:12px;"><span style=3D"font-family:luci=
da sans=20
unicode,lucida grande,sans-serif;"><a a=3D""=20
href=3D"mailto:me@MyDomain.com"=20
style=3D"font-family:'Lato',arial,sans-serif;color:#404040;font-size:13px;t=
ext-decoration:none;">me@MyDomain.com</a></span></span></div>
=09=09=09<div style=3D"padding-bottom:5px;">
=09=09=09=09<span style=3D"font-size:12px;"><span style=3D"font-family:luci=
da sans=20
unicode,lucida grande,sans-serif;"><a=20
href=3D"http://www.MyDomain.com"=20
style=3D"color:#870ee3;font-size:13px;text-decoration:none;font-family:'Lat=
o',arial,sans-serif;"
target=3D"_blank"><span style=3D"color:#303371;"><span>Shop MyDomain </sp=
an></span></a></span></span></div>
=09=09=09<table style=3D"border-spacing: 0px;max-width:108px;">
=09=09=09=09<tbody>
=09=09=09=09=09<tr>
=09=09=09=09=09=09<td style=3D"background-color:#303371;border-radius:20px"=
=20
align=3D"center" height=3D"20" width=3D"20" valign=3D"middle">
=09=09=09=09=09=09=09<a href=3D"https://www.facebook.com/MyDomain/" target=
=3D"_blank"><img
=20
src=3D"https://www.sellerpanda.com/email_signatures/app/public/images/2/fac=
ebook.png"
style=3D"max-width:20px;max-height:12px;vertical-align: middle;"></a></td>
=09=09=09=09=09=09<td width=3D"5">
=09=09=09=09=09=09=09=C2=A0</td>
=09=09=09=09=09</tr>
=09=09=09=09</tbody>
=09=09=09</table>
=09=09</div>

=09=09
<p>
=09=09=09=C2=A0</p>

=09

</div></div>
</body>
</html>

So, Zoho email via Postbox signs the Content-Type AND Content-Transfer-Encoding.

Zoho email via Zoho.com and Outlook signs only the Content-Type, then changes the encoding, and changes the email to multi-part emails.

Yes, I have tried changed the encoding in both Zoho AND Outlook, but regardless of what I set them too, this issue replicates.

Please research and advise asap, thank you.

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