I've implemented a very common approach to email open rate tracking using a 1x1px transparent image:
<img src="https://myserver/trackresponse?source=1&action=1"
style="border:0;width:1px;height:1px;" alt="" />
And the php code to track response and return the image looks like this:
header('Content-Type: image/png');
(Record response on DB)....
$im=imagecreatefrompng("/images/pixel.png");
imagepng($im);
imagedestroy($im);
On viewing the email the request for the image is executed (I know this as the the response is recorded on the DB).
Although Gmail (webmail and iphone app) and even Outlook.live.com displays the email correctly (as in you can't see the tracking pixel), the Windows mail app (Windows 10) displays this:
Any ideas?
