If you have set an align attribute in an image to right or left, Thunderbird will add a 3 pixel margin these images.
When using align=”right” Thunderbird will add a 3px margin to the left of the image, where using align=”left” Thunderbird adds a 3ps margin to the right of the image.
To fix this issue, you can either remove the align attribute or using CSS add margin:0; to each image with an align attribute.
HTML
<img src="http://www.htmlemailcheck.com/assets/img/og-logo.png" width="500" height="300" align="right" style="margin:0;">
