Image Blocking in Email Clients: Current Conditions and Best Practices

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. As Nitin Lodha points out, according to a study by Team Chitrangana 30% of your recipients don’t even know that images are disabled. 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.

Default Settings in Popular Email Clients

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 I’m reporting the settings of my personal versions of each client and that settings may differ from one version to another.). I have included contextually-relevant references to ALT text as part of this article. For a more in-depth look at how ALT text renders in popular email clients, you may want to read a more comprehensive article I wrote about ALT text.

Image Blocking in Webmail Clients
Client	Default Img Display	Trusted-Sender Img Display	Renders ALT Text
Yahoo Mail	on
Yahoo Mail Beta	on
Windows Live Mail	off
Gmail	off		sometimes
.Mac	on		sometimes
Hotmail	on
AOL	on

Image Blocking in Desktop Clients
Client	Default Img Display	Trusted-Sender Img Display	Renders ALT Text
Apple Mail	on
Thunderbird	on
Outlook 2007	off		sort of
Outlook 2003	off
Outlook Express	on
Lotus Notes	on
Eudora	on		sort of
Entourage	on
AOL	off

So now that we’ve covered the settings in popular email clients, let’s outline how we can help our emails survive image blocking.

Recommendations for Successful Deployment

From my 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

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.

Prepare for Disabled Images

So we’ve created a structurally-sound template, we’re preparing to send our email to a permission-based list of subscribers and we’ve taken steps to see our list email-address into the address books of the said subscribers. There are still a number of people on our lists who will intentionally block images, and therefore we should account for that scenario.

I wrote an article outlining a technique for this very purpose. With the releases of Yahoo Mail Beta and Windows Live Mail we lose the ability to integrate the aforementioned technique. However, Ryan Kennedy from the Yahoo Mail team has pointed out that they are looking into potential resolutions for this obstacle.

Positioning aside, there are some things we can do to retain the integrity of our emails when images are disabled:

• Begin an email with HTML text or logical ALT text. We can decide what a reader sees in a preview pane or small message-window. If we’re prepared, we can optimize the experience of scanning messages. Moreover, some applications offer the ability to preview the first few lines of text before an email is loaded/viewed.

• Use ALT text. This seems so obvious I’m almost embarrassed mentioning it. However, I don’t have enough fingers and toes to count the email newsletters I receive sans ALT text, so there it is.

• Use captions for contextually-important images. In lieu of proper support for ALT text across the board, we can add captions to images which are vitally important to the content of an email.

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.