The consensus is that while image-only emails may not always be detrimental to deliverability, they present several challenges. B2C providers focus on UX and engagement, while B2B filters sometimes scrutinize the image-to-text ratio. Spam filters can struggle with image-only emails because they can't read the content effectively, and spammers often use images to hide malicious links. Accessibility is a major concern, as screen readers can't interpret images without alt text. Large, unoptimized images can slow loading times, impacting user experience and potentially triggering spam filters. While some experts downplay the text-to-image ratio, a lack of text can hinder content understanding by filters. Overall, deliverability relies on comprehensive sending practices, not just image usage. Essential aspects also include email consent, list hygiene and correct email authentication.

While not always a definitive cause of deliverability issues, sending image-only emails presents several potential problems. Major B2C providers prioritize user engagement and UX, but B2B filters may penalize a high image-to-text ratio. Image-only emails can be flagged as spam because email clients cannot read the content effectively, spam filters struggle to parse them, and they often lack accessibility for screen readers. Slow loading times from large images can also negatively impact user experience. Although not strictly essential, there are a number of other considerations when sending emails in bulk to ensure good deliverability. These include consent, list hygiene and correct email authentication.

The impact of image-only emails on deliverability is nuanced. While some spam filters might penalize them, this doesn't always translate to significant deliverability issues. Experts highlight the importance of accessibility and ensuring content fails gracefully when images don't display. Poorly designed image-only emails can present issues on both desktop and mobile, necessitating careful design. Some sources refute the idea that text-to-image ratio is a primary spam filtering factor, emphasizing a more comprehensive approach to sending practices and engagement metrics. However, other experts suggest that a lack of text can make it harder for filters to understand the content, potentially leading to deliverability problems.

While Gmail doesn't explicitly penalize image-heavy emails, a good balance of text and images is recommended. Excessive images can trigger spam filters as spammers use them to conceal malicious links or bypass text-based detection. SpamAssassin includes rules to assess image-to-text ratios, increasing the spam score for emails with high image content, which can affect deliverability. Microsoft Postmaster advises careful design of image-heavy emails, ensuring they don't obscure the message or hide malicious links, which can harm sender reputation and deliverability to Outlook.com users. Some spam filters check the text-to-image ratio, as imbalances can obscure the content and aid spammers in bypassing filters.