Do email spam filters scan image content and QR codes?
Summary
What email marketers say9Marketer opinions
Email marketer from Email Geeks shares that Proofpoint does QR analysis.
Email marketer from EmailOctopus explains that using descriptive alt text for images is crucial. Spam filters often look for missing or irrelevant alt text as a sign of spam.
Email marketer from Mailjet shares that while text is heavily scrutinized, images are also scanned for suspicious elements. They recommend optimizing images and using alt text.
Email marketer from Moosend responds that QR codes can be a red flag for spam filters, especially if they link to unfamiliar or suspicious domains. They recommend using QR codes sparingly and ensuring they link to reputable sites.
Email marketer from Litmus shares that large image sizes can trigger spam filters. Optimizing images for size and resolution is essential for deliverability.
Email marketer from StackOverflow explains that Spamassassin does check images.
Email marketer from Reddit explains that using images instead of text to by-pass spam filters doesn't work any more - OCR is used now so it will likely trigger.
Email marketer from Sender.net answers that spammers sometimes embed entire messages as images to bypass text-based filters. They suggest using a balance of text and images.
Email marketer from Reddit says to be careful embedding QR codes as links in emails - spam filters flag these as suspicious and can be detrimental to sending reputation.
What the experts say5Expert opinions
Expert from Spam Resource explains that spammers have employed image-based spam, embedding text within images to evade traditional text-based filters; however, modern spam filters utilize OCR to analyze these images.
Expert from Email Geeks explains that scanning images in any useful way is fairly expensive.
Expert from Email Geeks explains that if the mail is DMARC passing from a known entity with an incredibly high one-off volume of mail, they're unlikely to do a lot of analysis on content.
Expert from Word to the Wise explains that some filters look for text within images using OCR and can flag messages if the text is suspicious or if the image-to-text ratio is too high. Also adding that including a QR code is pretty suspicious
Expert from Email Geeks explains images are scanned for various things and in various ways.
What the documentation says4Technical articles
Documentation from Apache explains that it is possible to configure Spamassassin to check images using OCR.
Documentation from Spamhaus indicates that advanced spam filters use optical character recognition (OCR) to analyze images for text content and identify potential spam indicators.
Documentation from Microsoft Learn indicates that Exchange Online Protection scans images for malicious code and content that violates their policies, contributing to spam and malware filtering.
Documentation from Google Workspace Admin Help explains that Gmail's spam filters analyze images for suspicious content, including embedded text and unusual patterns, contributing to overall spam detection.