Image blocking occurs when recipients’ email clients block images in emails, which is usually done for security reasons. Recipients can also choose to block images from automatically downloading because of low internet bandwidth.
Brands can optimize emails with regard to image blocking by adding alt text and using bulletproof call-to-action (CTA) buttons by encoding with HTML, performing email testing to ensure CTAs and links display, and providing context to recipients even when email clients block images.
At Email on Acid, we don’t recommend sending image-only emails as these emails can cause accessibility and deliverability issues for senders, like screen readers can only access alt text in emails.