Set the width/height of the open beacon image to avoid red cross

Edit Subject

At the moment although the beacon image is 1px x 1px, until the user authorises the sending domain in their email client it's shown as the dreaded red cross.

This can be avoided by simply setting the width/height of the image in the HTML, I've added Campaign Monitor's HTML and SendGrid's below for comparison:

SendGrid (red cross):

<img src="http://...image.gif" alt="">

Campaign Monitors (no red cross):

<img src="https://.../o.gif"  width="1" height="1" border="0" style="height:1px !important;width:1px !important;border-width:0 !important;margin-top:0 !important;margin-bottom:0 !important;margin-right:0 !important;margin-left:0 !important;padding-top:0 !important;padding-bottom:0 !important;padding-right:0 !important;padding-left:0 !important;" >

I'm not sure the additional style settings are necessary as they're just to override any settings you might be doing within your HTML but it wouldn't hurt to add it too.