Why is this HTML adding a horizontal line to Outlook Emails?

I'm deploying an email for a client that is pretty straight forward. But for some reason Outlook adds a horizontal line between 2 tables. I cannot for the life of me figure out why.

horizontal line example

Code in question:

<!--[if (!mso)&(!IE)]><!-->
<div style="border-top:5px solid #D9d9d9; border-left:5px solid #D9d9d9; border-bottom:5px solid #D9d9d9; border-right:5px solid #D9d9d9; padding-top:0px; padding-bottom:10px; padding-right: 0px; padding-left: 0px;">
    <!--<![endif]-->
    <div class="img-container center  autowidth  fullwidth" align="center" style="padding-right: 20px;padding-left: 20px;">
        <!--[if mso]><table width="100%" cellpadding="0" cellspacing="0" border="0"><tr style="line-height:0px"><td style="padding-right: 20px;padding-left: 20px;" align="center"><![endif]-->
        <div style="font-size:1px;line-height:20px">&nbsp;</div><a href="" target="_blank" tabindex="-1"> <img class="center  autowidth  fullwidth" align="center" border="0" src="" alt="Image" title="Image" style="text-decoration: none; -ms-interpolation-mode: bicubic; height: auto; border: none; width: 100%; max-width: 183px; display: block;" width="183"></a>
        <div style="font-size:1px;line-height:15px">&nbsp;</div>
        <!--[if mso]></td></tr></table><![endif]-->
    </div>
    <!--[if mso]><table width="100%" cellpadding="0" cellspacing="0" border="0"><tr><td style="padding-right: 10px; padding-left: 10px; padding-top: 10px; padding-bottom: 10px; font-family: Arial, sans-serif"><![endif]-->
    <div style="color:#555555;font-family:'Open Sans', Helvetica, Arial, sans-serif;line-height:1.2;padding-top:10px;padding-right:10px;padding-bottom:10px;padding-left:10px;">
        <div style="line-height: 1.2; font-family: 'Open Sans', Helvetica, Arial, sans-serif; font-size: 12px; color: #555555; mso-line-height-alt: 14px;">
            <p style="font-size: 12px; line-height: 1.2; text-align: center; mso-line-height-alt: 14px; margin: 0;"><span style="font-size: 16px; color: #000000;">Efficient Refrigerators</span></p>
        </div>
    </div>
    <!--[if mso]></td></tr></table><![endif]-->
    <!--[if mso]><table width="100%" cellpadding="0" cell[spacing="0" border="0"><tr><td style="padding-right: 10px; padding-left: 10px; padding-top: 10px; padding-bottom: 10px; font-family: Arial, sans-serif"><![endif]-->
    <div style="color:#555555;font-family:'Open Sans', Helvetica, Arial, sans-serif;line-height:1.2;padding-top:10px;padding-right:10px;padding-bottom:10px;padding-left:10px;">
        <div style="line-height: 1.2; font-family: 'Open Sans', Helvetica, Arial, sans-serif; font-size: 12px; color: #555555; mso-line-height-alt: 14px;">
            <p style="font-size: 12px; line-height: 1.2; text-align: center; mso-line-height-alt: 14px; margin: 0;"><span style="color: #808080; font-size: 12px;"><span style="font-size: 12px;">Choose efficient and save up to $240 a year in energy costs!</span></span></p>
        </div>
    </div>
    <!--[if mso]></td></tr></table><![endif]-->
    <!--[if mso]><table width="100%" cellpadding="0" border="0"><tr><td style="border-collapse: collapse; padding-right: 10px; padding-left: 10px; padding-top: 10px; padding-bottom: 10px; font-family: Arial, sans-serif"><![endif]-->
    <div style="border-collapse: collapse; color:#555555;font-family:'Open Sans', Helvetica, Arial, sans-serif;line-height:1.2;padding-top:10px;padding-right:10px;padding-bottom:10px;padding-left:10px;">
        <div style="font-family: 'Open Sans', Helvetica, Arial, sans-serif; font-size: 12px; line-height: 0; color: #555555; mso-line-height-alt: 14px;">
            <p style="font-size: 12px; line-height: 1.2; text-align: center; mso-line-height-alt: 14px; margin: 0;">Compare Deals and</p>
            <p style="font-size: 12px; line-height: 1.2; text-align: center; mso-line-height-alt: 14px; margin: 0;"><strong><span style="color: #000000; font-size: 12px;"><span style="font-size: 22px;">Save Big!</span></span></strong></p>
        </div>
    </div>
    <!--[if mso]></td></tr></table><![endif]-->
    <!--[if mso]><table width="100%" cellpadding="0" border="0" style="border-spacing: 0; border-collapse: collapse; mso-table-lspace:0pt; mso-table-rspace:0pt;"><tr><td style="border-collapse: collapse; padding-top: 10px; padding-right: 10px; padding-bottom: 10px; padding-left: 10px" align="center"><v:roundrect xmlns:v="urn:schemas-microsoft-com:vml" xmlns:w="urn:schemas-microsoft-com:office:word" href="" style="border-collapse: collapse; height:27.75pt; width:126pt; v-text-anchor:middle;" arcsize="60%" stroke="false" fillcolor="#307298"><w:anchorlock/><v:textbox inset="0,0,0,0"><center style="color:#ffffff; font-family:Arial, sans-serif; font-size:14px"><![endif]-->
    <div class="button-container" align="center" style="padding-top:10px;padding-right:10px;padding-bottom:10px;padding-left:10px;">
        <a href="" target="_blank" style="-webkit-text-size-adjust: none; text-decoration: none; display: inline-block; color: #ffffff; background-color: #307298; border-radius: 22px; -webkit-border-radius: 22px; -moz-border-radius: 22px; width: auto; width: auto; border-top: 1px solid #307298; border-right: 1px solid #307298; border-bottom: 1px solid #307298; border-left: 1px solid #307298; padding-top: 0px; padding-bottom: 5px; font-family: 'Open Sans', Helvetica, Arial, sans-serif; text-align: center; mso-border-alt: none; word-break: keep-all;"><span style="padding-left:20px;padding-right:20px;font-size:14px;display:inline-block;">
                <span style="font-size: 16px; line-height: 2; mso-line-height-alt: 32px;"><span style="font-size: 14px; line-height: 28px;"><strong><span style="line-height: 28px; font-size: 14px;">Compare Products</span></strong></span></span>
            </span></a>
    </div>
    <!--[if mso]></center></v:textbox></v:roundrect></td></tr></table><![endif]-->
    <!--[if (!mso)&(!IE)]><!-->
</div>                                      
<!--<![endif]-->