Image-Blocking Scorecard, Part 1

It’s been over two years since e-mail marketers began worrying about blocked images in their messages. Back then, my colleagues Kirill Popov and Loren McDonald wrote what I still consider the definitive column about this new challenge.

So where are we today?

I got to experience firsthand how effectively e-mail marketers have risen to this challenge when I got a new computer and upgraded (finally!) to Outlook 2003. Although I’d transferred my contacts list, I still found images in most e-mail blocked by default.

The good news: it was much easier than I had expected to get Outlook to show me what I was missing, although it did take two or more clicks.

The bad news: e-mail marketers haven’t adjusted their creative to address this two-year-old challenge.


This isn’t a formal market research study, but I did try to make it as fair and representative as possible. I took a sample of 30 commercial HTML e-mail messages — a mix of 14 business-to-business (B2B) and 16 business-to-consumer (B2C) — from 30 different organizations. All were delivered to my inbox in early December; with the holidays, I had no shortage of messages from which to choose. Most came from recognizable names, either large consumer retailers, companies providing services to businesses, or industry organizations selling products. I ignored e-mail newsletters, focusing on standalone promotional messages.

I viewed the messages solely in the preview pane, as many users do. My reading pane was a generous 4in. x 10in. I haven’t changed my screen resolution from the default 1,024 x 768 pixels on a 17in. monitor.

Scope of Image Blocking

In 80 percent of the samples, one or more images were blocked; they appeared as the dreaded red “x.” The remainder of the messages didn’t have any images in the preview pane, even though they were in HTML. That’s not necessarily a bad thing, so long as there’s copy to engage readers. Here’s the breakdown:

ClickZ Graphic

Most of the non-image messages fell into the B2B category. Twenty-nine percent of the B2B messages included no images, so no blocked images in the preview pane. Compare that with just 13 percent of B2C messages with no images.

One B2C e-mail had 12 blocked images in the preview pane alone! On average, 2.5 images were blocked per message. But again, B2B e-mail fared better than B2C e-mail. In the B2B category, an average of 1.1 images per e-mail were blocked; in the B2C sample, the figure was 3.8.

What might explain the variance?

B2B e-mailers are used to dealing with a wider variety of e-mail clients than B2C. The one that immediately comes to mind is Lotus Notes, a favorite of Fortune 500 IT departments that’s not widely in use in the consumer world. Lotus Notes is infamous for blocking images by default (it’s done so for years, way before Microsoft Outlook got on the bandwagon).

Even when readers configure Lotus Notes to read HTML, it’s problematic. HTML that renders properly in every other e-mail client can blow up when viewed in Lotus Notes. As a result, B2B e-mail marketers may be more cautious than B2C folks about using images in their e-mail.

Alt Tag Use

One of Kiril and Loren’s recommendations for dealing with blocked images is to use alt tags. Alt tags are text phrases you can program to appear next to the red “x” in blocked images. If the image is a picture of an Audi S4 convertible, the alt tag might read “Audi S4 convertible.” More important, if the image doubles as your headline and says “Save 50% — Today Only,” your alt tag should carry the same message in text.

Of the messages with images, only 38 percent included alt tags. B2C e-mail was more likely to have alt tags (44 percent); only 14 percent of B2B e-mail featured them.

This may not be as big an issue as it appears. In addition to blocking images, Outlook includes this message as an alt tag after each red “x”: “Right-click here to download pictures. To help protect your privacy, Outlook prevented automatic download of this picture from the Internet.”

It’s a mouthful. And it precedes any alt tag text the sender might have included. So even when there were alt tags, they weren’t prominently placed or easy to read or skim. Based on this, the value of alt tags is minimal. I’m not sure I’d bother.

But if I did bother, I’d make them relevant, which the mailers in this sample did pretty well. Seventy-eight percent of those who included alt tags leveraged them fully. In the B2C sample, 86 percent were helpful and relevant, compared to just 50 percent of those in the B2B sample.

What’s a good alt tag?

“Click Me” wasn’t high on my list. Sounds a lot like “drink me” from “Alice in Wonderland.” And it does lead you down a rabbit’s hole, as this particular e-mail gave me no idea where the link would lead.

More useful were alt tags that included the sender’s brand name or URL (“”) or that spelled out the key offer (“Upgrade now for just $30”).

Next Time

In part two, I’ll continue my analysis, looking at visible headlines, calls to action in the preview pane, links to view online, requests for whitelisting, and ability to communicate without images (the biggie!).

Until then, best wishes for happy holidays and a great start to the New Year.


Want more e-mail marketing information? ClickZ E-Mail Reference is an archive of all our e-mail columns, organized by topic.

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