What is image blocking?
If you hang around any discussion of email design and production, the terms "image blocking" or "image suppression" will appear at regular intervals. But what do those terms mean? How does image blocking impact email marketing? And how can you meet the challenge? Read on for the answers...
What are blocked images?
The software (e.g. Thunderbird) or service (e.g. Yahoo! Mail or your corporate IT department) that manages your incoming email invests a lot of effort in keeping spam out of your inbox.
Previously, most technologies for identifying (and then deleting or rerouting) spam looked at the text of the message for clues. They were pretty good at spotting the "bad" messages this way.
Unfortunately, spammers adapted. Some started replacing some (or all) of their email's text with a small piece of code that calls up a remote image from another computer on the Internet and displays it in the email.
The "clever bit" is that this image contains text, working much like a photo of a page of words would.
Since anti-spam technologies find it more difficult to "read" words displayed as a picture, rather than typed out in an email, so-called "image spam" was initially more successful in getting unsolicited messages in front of email users.
Software manufacturers and email services thus started to see images with a somewhat jaundiced view.
Now throw in two other problems:
First, spammers also began sending explicit images to accompany their adverts for male enhancement treatments or adult services. The kind of images that children (and others) really shouldn't see.
Second, images also became potential security threats. In certain circumstances, images in an email could work as a conduit for installing malicious, unwanted software on the recipient's computer.
To counter these potential problems, many email software packages or webmail services no longer display an image automatically when an email is viewed. Instead, they block the call to display that image and replace it with some kind of placeholder.
This process is known as image blocking or image suppression.
How does it look in practice?
Different email services and software have different ways of blocking images. For example, one might block images by default, another might require the user to turn on image blocking first. One might use a small red cross as a placeholder, another a grey rectangle.
Of course, nobody wants to ban images completely from email. So all (as far as I know) services and software do provide some kind of feature letting the user "turn images on" for a specific email or for emails from a specific sender.
Often, emails from anybody in the user's address book bypass the image blocking feature. The new Yahoo! Mail, for example, lets users manually activate images on any single email whose images were suppressed. It also lets users choose between 3 default suppression options:
- Display all images in email, except for those in the spam folder
- Display images only in emails from contacts or certified senders
- Block all images initially
Let's look at some examples...
Here's how my website logo displays in an email sent to a Yahoo! Mail account:
At the top of the message, I have the option to turn the image on:
And here's what it would then display:
Here's another example of what a blocked image can look like, this time from the Thunderbird desktop email software:
Again, with an option to unblock the image:
Email marketing impacts
Image blocking is a widespread feature. It is entirely possible that the majority of people getting your commercial emails are using email software or a webmail service that blocks images.
Why is this a problem?
If your email's design and content is based largely on images, then it can look very strange when images are blocked. The particular placeholders used by the email service or software in question can play havoc with your nice layout, shunting text into the wrong place and other such misdemeanors.
Worse, if important information (e.g. headlines, descriptions of offers) or links (e.g. a "click here" or "buy now" button) take the form of images, then they may never get seen, read or acted on.
Suppressed images can also hinder proper recording of some of the statistics returned in your email campaign reports: see the guide to open rates for more information.
Clearly image blocking is a challenge for email marketers.
Email marketing solutions
Fortunately, there are various tactics you can use to counter the effects of image blocking. Browse through the outline below and then visit the main image blocking category for more detail on the important nuances of both basic and advanced techniques.
1. Include height, width and alt attributes
The code that calls for an image in an email looks something like this:
<img src="http://edrf.com/images/block1.jpg" />
This tells the software or service to visit the edrf.com website and dig down to find the block1.jpg image file, then display it in the email.
There are various other bits of information you can put in that code that describe how to display the image. For example, the height and width attributes...
<img src="http://edrf.com/images/block1.jpg" height="25" width="600" />
...let the email software or webmail service know how big a space to reserve for the image: in this case, 25 pixels high by 600 pixels wide. Most (but not all) of the time, this means that the raw layout of your page will be preserved, even if the image itself isn't displayed in the reserved space.
This helps avoid shunting around of your carefully laid out paragraphs, columns, etc.
The alt attribute...
<img src="http://edrf.com/images/block1.jpg" alt="Picture of the Queen" />
...provides alternative text for display when the image is unavailable. Many email software packages and webmail services will display this text in place of the blocked image:
Clever use of the alt attribute can encourage people to unblock the images, and better understand the message or where they might usefully click.
2. Balance images with text
Most experts recommend a mixture of text and images in your email. Enough of a balance so that the loss of images doesn't prevent people "getting" the message.
It's often tempting, for example, to use a large single image for your emails. Maybe recycle a brochure. But image blocking means a large number of recipients will then likely see absolutely nothing but an empty box or a red cross.
In particular, it's important to ensure that really key information (such as links) are also visible in text form. This means that recipients still have access to this information when images are blocked.
This email from Apple, for example, features text links immediately under the "related music" images, so recipients can still make an informed decision on where to click, even if the images are suppressed:
3. Use a design testing service
Whatever you choose to do, it's worth running your email through a design testing service (as cheap as $5 a pop). Many of these let you see screenshots of how your email appears in major email software and at common webmail services when images are blocked or suppressed.
You can use the insights to make any necessary design changes.
4. Web version links, address book entries and safe senders
With all the variety out there in the email world, you can never be sure that your email will be readable to every recipient. One option is to include a link right at the top of your email to a "web version" or similar:
The link takes people to a copy of the email on a web page. So if they can't make head or tail of your message when viewed in their email software or at their webmail service, they can see a nice version via their standard web browser.
Some marketers also choose to encourage recipients to add a particular address to the recipient's address book or list of safe senders. As we learnt above, email sent from that address would then be exempt from image blocking if the recipient uses a webmail service like Yahoo! Mail or email software like Thunderbird.
5. Consider email certification
Email certification is where you pay a third-party service to certify your emails as reaching some particular quality standard. Emails accredited in such a way may be given priority treatment by organizations managing incoming email. A common benefit is for these certified emails to bypass image blocks.
For example, emails accredited by the Sender Score Certified program show up with images intact at the Windows Live Hotmail webmail service. Those accredited by Goodmail Systems preserve their images at, for example, Yahoo! Mail.
For more information on email certification, read this article.
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