Do images in emails trigger spam filters and how does email fingerprinting work?

Email marketer from Email Geeks shares an experience where a client received a fingerprint on an image because the image was included in other messages that drove spam complaints, the data associated with the fingerprint decides if the fingerprint will impact the stream negatively.

Email marketer from Reddit r/EmailMarketing shares that using links to suspicious or blacklisted image hosting sites can trigger spam filters, regardless of the image content itself.

Email marketer from Mailchimp Resource Center shares that while images themselves aren't usually the primary trigger for spam filters, very large images can contribute to deliverability issues, particularly if the email lacks sufficient text content.

Email marketer from Sender.net Blog explains that missing or irrelevant alt text for images can be a red flag for spam filters, as it hinders accessibility and can be seen as an attempt to hide content.

Email marketer from MailerLite shares that including descriptive alt text to images is essential, it not only improves accessibility but also ensures that if the image doesn't load, there's context, reducing spam risk.

Email marketer from Litmus Blog shares that where you host your images matters. Using a reputable CDN or your own domain is better than free image hosting, which can be associated with spam.

Email marketer from Email on Acid Blog shares that having a high image-to-text ratio can negatively impact deliverability, as spam filters may see it as an attempt to bypass text-based analysis. Recommends using a balanced ratio.

Email marketer from StackExchange mentions that images with embedded text are now commonly scanned and OCR'd for suspicious keywords, making them less effective at bypassing spam filters.

Email marketer from Campaign Monitor shares that large images in emails can trigger spam filters as they can slow down the loading time of emails, which can lead to a negative user experience, potentially resulting in spam complaints.

Email marketer from SparkPost shares that a low text-to-image ratio could trigger spam filters, recommending including enough text to give context and signal legitimacy.

Expert from Email Geeks shares that fingerprinting is the simplest, most dumbed-down, highest performance implementation of a general multi-dimensional vector search. It is used to cluster similar emails together and treat them as a group, is a universal thing in modern mail filtering.

Expert from SpamResource shares that while simple image analysis is not typical, sophisticated filters can perform OCR (Optical Character Recognition) on images to detect spammy text embedded within them.

Expert from Email Geeks explains that Cloudmark fingerprints everything that comes through its network and uses fingerprints as a content filter.

Expert from Email Geeks notes that images can be part of the overall message fingerprint used by entities like Cloudmark to identify similarity between content, so doing A/B test could look different to Cloudmark.

Expert from Word to the Wise indicates that email fingerprinting involves identifying and tracking patterns in message content (including images), sender behavior, and infrastructure to identify and block spam campaigns.

Expert from SpamResource explains that using images hosted on domains with a poor reputation can negatively impact deliverability, even if the image content is harmless.

Expert from Email Geeks shares that spam filters don't typically analyze images much. They focus more on mail streams, links, hostnames, and text within the body of the email.

Expert from Email Geeks elaborates that the representation of an email is "lossily" with minor changes to the body not changing the fingerprint.

Expert from Email Geeks explains that a fingerprint is a short representation of the whole content of the email and is a way to condense an email into a short pattern that makes it easy and fast to compare.

Documentation from Microsoft 365 Defender documentation explains that its email filtering system analyzes various signals, including content fingerprints and sender reputation, to determine if a message is spam. Consistent sending patterns and content are key to establishing a good reputation.

Documentation from SpamAssassin Wiki explains that it uses various techniques, including fuzzy hashing (similar to fingerprinting), to identify near-identical messages. This helps in detecting spam campaigns that use slight variations of the same content.

Documentation from Cisco Email Security Documentation responds that fingerprinting involves creating a unique hash or signature of an email's content, including text, images, and attachments. This fingerprint is then used to compare against known spam signatures.

Documentation from RFC-Editor responds to the question of email fingerprinting and its techniques - explaining that it calculates a hash value from different parts of the email which is used to check if the email is a variant of spam or a known good email.

Documentation from Barracuda describes how its systems use fingerprinting to analyze zero-day exploits, including those potentially embedded in images.