We currently send newsletters through our website. We use our Zoho email to send us the Template.. in the template the images are there but in the actual email i send to myself half the images are missing

I have numerous emails to test on and yahoo and hotmail are working fine.

what causes the images to become broken or blocked? all images are JPEG

Zoho and gmail are not. Does anybody have any idea how i can fix the issue?

This is a new issue as previous newsletters have been working fine.