Image Blocking in HTML Email
Many people, either by email client defaults or personal preference, are blocking images in the HTML-formatted messages they are accepting. And then there are a small number of people who block HTML entirely. According to a study by Merkle in 2009, only 48% of email recipients see images automatically… In any case, it’s logical for recipients to block images and good practice for us to prepare for this scenario.
So what happens to our emails when images are blocked? What are the best practices for ensuring accessibility and optimizing presentation therein? What are default settings across the board? Let’s get down to answering these questions.
Yes! Proceed with caution. We should be giving serious consideration to image-blocking and what we can do about it. It’s natural and reasonable why people disable them, but with the right approach we can improve the experience for our subscribers.
Default email client settings
Every client has its own default settings regarding displaying/hiding images. And while most email clients have a setting to turn images on or off, some offer conditional settings which are contingent upon known senders or other factors. The following table outlines the default settings of popular desktop- and webmail-clients. (Note that We are using the settings of our own versions of each client and that settings may differ from one version to another).
Recommendations for Successful Deployment From a designers perspective, an email is successful when it meets the following goals:
- Retains visual integrity in the most commonly used email clients with images enabled.
- Retains readability in the most commonly used email clients with images disabled.
- Is readable to people with visual disabilities and navigable to people with mobility disabilities.
- Is low in weight for recipients using mobile devices and dial-up connections.
- Is deployed to a permission-based list of subscribers.
- Meets CAN-SPAM Act requirements.
- Legitimately passes common tests employed by spam filters.
Looking at this list it becomes clear just how important it is to consider image blocking when designing/developing an email. Dependency on images can lead to failures on many different levels. Preparing for a scenario in which images are disabled puts us at an advantage to oblige the settings/preferences of a broader range of recipients.
Become a “Known Sender”
Nearly every email client in my test suite enables people to automatically display images when a message is from a “known sender” (senders appearing in white lists, contact lists or address books). Because our subscribers have requested to receive emails from us, they will naturally want to ensure they receive the messages. Spam filters can disrupt legitimate communication when subscribers are unaware of how they function. With a couple, simple notifications we can increase our chances of success:
- Ask a subscriber to add the email-list address to their address book (right on the subscribe form) and briefly explain why.
- Enable a double opt-in subscription process, and send a plain-text confirmation which includes a request to add the email-list address to a recipient’s address book. And, again, briefly explain why.
Informing a subscriber about this simple step will increase our chances of images being enabled and will help us legitimately pass through spam filters.
Avoid Image-Based Emails
Again, this is something which should seem obvious. But image-based emails are often practiced as a simple, easy method of delivering a pretty design irrespective of the rendering circus among the array of common email-clients. When we ponder image blocking as part of the rendering equation, it’s easy to see how an image-based email could be completely destroyed with a single preference.
Furthermore, this doesn’t take into consideration file sizes for mobile/dial-up recipients, accessibility for those visually impaired or the HTML-to-text ratio that popular spam filters apply with their algorithms. In summary, we should be giving serious consideration to image-blocking and what we can do about it. It’s natural and reasonable why people disable them, but with the right approach we can improve the experience for our subscribers.
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