Amazon SES tracking transparent GIF not opened in Zoho mail

Amazon SES tracking transparent GIF not opened in Zoho mail

Using Amazon SES for email marketing, they use a tracking transparent gif like:

<img alt="" src="http://pp9hjm8c.r.eu-west-1.awstrack.me/I0/0102016ebbe1bea6-f44704ec-6675-4061-a9f6-e498ec30d67b-000000/p4OxlOJSsV3FXWCM_2Ef0kOWuQQ=138" style="display: none; width: 1px; height: 1px;">

Even when you click "Display now - External Images are not displayed" the tracking image is still not loaded. If I load the url of the image manually, it triggers the tracking correctly.