Do spam filters hate images?

You've probably heard it: "Don't use too many images or you'll land in spam." It's one of those email myths that won't die. The truth is a bit more nuanced than that.

Spam filters don't hate images. What they do flag is emails where images are doing all the work and text is doing none of it. A classic old-school spam trick was to put the entire message inside a single image so filters couldn't read the words. Filters caught on to that fast. So now they look at whether your email has enough readable text to actually analyze.

If your email is mostly images with almost no text, the filter has nothing to work with. That looks suspicious. It's not about the images themselves. It's about what's missing around them.

A rough guide for image-to-text balance:

• Aim for at least 60% readable text to 40% images. That's not a hard rule, but it's a safe starting point.
• Make sure every image has descriptive alt text. This helps filters read your content even when images are blocked, and it helps your subscribers who can't see images too.
• Never send an image-only email. Not one. Even a short header image with a paragraph of real text underneath is miles better than a single image with a button.
• Your preheader and opening paragraph carry weight. Put real, readable text up top.

Modern filters (think Gmail and Outlook) are sophisticated enough to evaluate your full sending history, your engagement rates, and your authentication alongside any content signals. One image-heavy campaign from a trusted sender probably won't hurt you. A pattern of low-text emails to an unengaged list? That's where things start to go sideways.

So no, images aren't the enemy. Just make sure your words are doing their fair share of the work too.

If you want to check whether your emails have other content signals that might be flagging filters, our free Subject Line Tester is a good place to start. Or if something's actively going wrong, drop us a message and we'll take a look.