What happens if an image is blocked by a spam filter?
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Your email sails through the spam filter and lands in the inbox. But your image doesn't. That's different from when subscribers block images themselves. A spam filter has flagged your specific image URL or content as risky and stripped it out.
Spam filters are paranoid about images for good reason. They've seen phishing attacks hide inside images. They've watched malicious domains use images to track victims. So they maintain lists of suspicious image URLs, blacklisted hosting domains, and pixel patterns commonly used in spam.
Here's what triggers filter blocking. Hosting images on a blacklisted domain (a server that's been flagged for sending spam or hosting malware). Using an image URL that's previously been flagged for phishing or scams. Embedding an image that's nearly all red or has pixel patterns that filter algorithms recognize as spam markers. Sending an email with images and almost no text (looks like you're hiding your message in the image).
The fix? Host images on reputable CDNs and trusted image hosting services. Include plenty of real text in your email. If you're unsure about your sender reputation, check it with Review My Emails' SOS hotline.
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