Hi,
I have used Zignatures in my email. Here is the html:
<div>
<table style="width: 250; font-family: Arial, sans-serif; font-size: 11px;">
<tbody>
<tr>
<td width="30" height="30"><img style="vertical-align: top; margin-right: 3px;" src="https://theme.zdassets.com/theme_assets/11229426/89198540fc0690d1fe5ea72369eec2678823beef.png" width="30" height="30" /></td>
<td valign="baseline"><span style="color: #333333; font-size: 12px; font-weight: bold; margin-top: 2px;">{{current_user.name}} </span></td>
</tr>
</tbody>
</table>
</div>
<div>
<div id="content" style="width: 250; font-family: Arial, sans-serif; font-size: 11px; font-variant: small-caps; margin-left: 2px; margin-top: 5px;"><span style="font-weight: bold; font-style: italic; color: #333333;">{{current_user.signature}}</span><br /><span style="font-weight: bold; font-size: 11px; color: #009966;">TEL:</span> {{current_user.phone}} <br /><span style="font-size: 11px; color: #009966;">Leuvensesteenweg 561, 1930 Zaventem</span><br /><a href="http://www.facq.be" target="_blank"><span style="color: #000000; font-variant: normal;">www.facq.be</span></a></div>
</div>

I've experimented with adding inline attributes to eliminate the border and have also tried achieving this with CSS. Additionally, I attempted to replace the table with 'div', but it appears that this approach is not effective because the CSS isn't being applied, preventing me from getting two divs inline. I also tried adding a whole html page and not just table element to see if css works in header and still no good.
Could you assist me in resolving this? It's crucial to address the border matter, as it looks rather peculiar.
Regards,
Ahmed Yar Zahid
It may be worth reaching out to the developer of this app directly to see if they can point you in the right direction. You can find their contact information in the app page here:
Zignatures
I hope this points you in the right direction!