Blocked E-Mail Images

If overzealous ISP and corporate spam filters don’t cause enough stress for permission-based email marketers, now we must deal with blocked images almost universally. In email clients that block images by default, such as Outlook 2003, a recipient can read an entire column (such as this one) either in the message preview pane or when it’s opened. The image-based ads and our dashing photo won’t appear (nor will the message be counted as opened). For publishers, advertisers, and e-tailers, this isn’t just a nuisance. It’s potentially costly.

The Blocked Images Issue

An estimated 95 percent of all commercial email messages are sent in HTML or in a multipart (combined HTML and text) format. Most email includes at least a single external image, even if it’s the open-tracking image, a clear, one-pixel GIF image used to track whether an email has been opened.

External images include logos, masthead or header images, and product or people photos. Virtually all email marketers host images on a Web server, rather than embed them within the message itself. To load images, a call is made back to the hosting server. Many ISPs and some email clients block this call.

The primary reasons behind image-blocking features are to enable users to prohibit pornographic images from loading and to prevent spammers from knowing if users open their messages. Gmail, for example, states: “Gmail disables images sent to you to protect you from unknown senders, like spammers, who use images and links to verify that your email address is real.”

The latest versions of many major ISPs’ email interfaces and email clients automatically block any external image (see table at the end of the column). In addition to Gmail, Microsoft’s recent Windows XP Service Pack 2 upgrade adds the blocked images feature to its Outlook Express client.

Implications for Permission Marketers

Disabled images have big implications for marketers, including:

  • Lower open rates. Some recipients scan email in the preview pane or open messages with images disabled. Marketers may have experienced a slight decline in open rates in the past year or so due to this.

  • Disabled banner ads. For ad-supported newsletters, disabled images means hosted ad formats aren’t displayed. Advertisers may see fewer impressions and click-throughs.
  • Image/content filter conundrum. Many e-commerce-oriented marketers who use aggressive promotional copy repeatedly throughout their messages have significant problems with content-based filters. To cope, some place much of their copy within images to avoid being filtered. This could increase delivery rates but result in fewer recipients actually seeing the copy.
  • Uncertainty caused by user-driven controls. Some ISPs and email clients enable users to determine if they want images blocked. So knowing which ISP a subscriber uses may shed little light on whether she has images enabled.

    Yahoo’s options, for example:

    • Don’t block any images

    • Block images in messages that SpamGuard thinks are spam
    • Block all images until I’ve had a chance to look it over

What Can Marketers Do?

A few steps marketers can take to help minimize the issue:

  • Get whitelisted. Some ISPs (notably AOL) and most managed mail networks can whitelist commercial mailers. This ensures selected email is allowed through with a minimum of filtering, image blocking included. In the business-to-consumer (B2C) environment, whitelisting usually happens at the user level. If a user added the sender’s address to her address book or “safe list,” your mail is unmolested by most ISP and personal filters.

  • Add a “view Web version” link. Host a version of your message on the Web. Provide a text link to it at the very top of your message. Regardless of image or personal settings, the recipient can always click through and view the message as a Web page.
  • Check message appearance in the preview pane. The preview pane is like a newspaper’s “above the fold” area and is where many recipients read or scan their messages. Can recipients can make a quick “open” decision based on content showing in the preview pane? If not, consider reformatting the message or adding teaser text up top that highlights what’s below.
  • Include alt tags. Although many email services and clients don’t display alt tags when images are disabled, it’s always a good idea to include them. Regardless of why, if images haven’t loaded, properly written alt tags at least provide the recipient with a sense of what she doesn’t see.
  • Use text-based ads. Publishers carrying server-based ads might consider including more text-based ads. Some publishers report text ads deliver higher CTRs than image-based ads.
  • Create text versions. With HTML email so popular, text versions tend to be neglected. Yet recent email client changes mean users have an increased ability to select which default format they prefer. A strong text version ensures you still reach users, regardless of format preference.
  • Include more text links. If your email includes several key linked images, consider adding text-based links above or below the image or appropriately placed in nearby copy.
  • Focus on CTRs and conversion rates. Don’t obsess over open rates. Monitor CTRs and conversion rates. Focus on maintaining or increasing them.

Blocked images should only be a minor nuisance for most permission email marketers who follow best practices and provide real value to recipients. Deliver the best, most relevant, personalized content to subscribers, and most will want to view your entire email with images, not just the text.

Till next time, keep on deliverin’.

Image Blocking by Major ISPs & E-mail Clients
Blocking Issue AOL
Gmail Hotmail Yahoo Outlook
w/o SP2
External images are blocked by default Yes Yes No No No Yes Yes No
User controls image-blocking settings Yes No Yes Yes Yes Yes Yes Yes
User clicks link to enable message’s images Yes Yes Yes No No Yes Yes N/A
Images enabled if sender is in user’s address book/buddy list Yes No Yes No Yes Yes Yes Yes
Images autoenabled if sender is on ISP whitelist Yes N/A Yes No N/A N/A N/A N/A
Alt tags displayed when images disabled No Yes No No No No No N/A
Preview window featured included No No No No Yes Yes Yes Yes
Note: SP2 = Service Pack 2 upgrade for Windows XP
Source: EmailLabs, 2004


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

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