Do image-only emails harm deliverability?

This is a question that I get asked often: If somebody sends an email message that is 100% images, does that design choice itself make the message more likely to get relegated to the spam folder? My short answer is no, not really, but it merits a discussion, so let's dive into it a little bit deeper.

First, let's get this bit out of the way -- YES, some spam filters will score emails higher (more spammy) if the image-to-text ratio is low – meaning that a message contains little text, but is chock full of images. SpamAssassin is an example of a filter that will note this in its filtering results. But while SpamAssassin can be good for “broad strokes” guidance for email senders, this is an example case where SpamAssassin’s filters give different results compared to the spam filtering engines of the biggest ISPs and mailbox providers like Gmail, Yahoo, or Microsoft. In other words, big image-heavy emails generally are not going to cause deliverability problems, regardless of what SpamAssassin says. And even in the case of SpamAssassin, this image-to-text ratio alone is not usually enough to cause a message to be treated as spam.

To me, the next biggest concern is accessibility. If you don’t properly implement alt text and make the emails navigable to those who can’t see your images, you’re going to end up with unhappy subscribers. Is it required that emails be ADA compliant? I’m not qualified to answer that, but I recommend you read this guide from the Bureau of Internet Accessibility (BOIA) for their thoughts and recommended best practices.

I’d go so far as to say that you MUST make sure that your images are navigable and legible with images off. And that includes ensuring visibility for your unsubscribe mechanism. If images have to be displayed for a subscriber to understand how they can unsubscribe, I question whether or not that email complies with US law. Even if somebody successfully argues that it’s legal, it’ll still result in more spam complaints, from subscribers unwilling to hunt through code to find an unsub link, when the “report spam” button is so easily found.

But, even though deliverability itself may not be a primary concern, and in theory you can address potential accessibility concerns, a lot of experts recommend against sending image-only marketing messages. Here’s what a group of smart marketers and deliverability consultants had to say on the topic when queried by Litmus’s Magan Le last year.

As a counterpoint, here’s solid guidance from Becki Francis of Moveable Ink, breaking down some of the myths around why people say you should avoid sending image-only emails.

I think if you take all of this guidance under consideration, it boils down to, it’s easy to do image-only emails wrong and it can take a lot of effort to do image-only emails properly. If you’re send image-only emails, deliverability will likely not present a challenge, but there are enough other ways things can go wrong that you still need to make sure that you’ve got the proper skill and capability to ensure that you get it right.

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