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What's Behind Gmail's 270% Bump in Email Opens?


By Justin Khoo

Looking at the latest Litmus email client marketshare report, something grabbed my attention. Gmail's market share number shot up to 10.3 percent from 3 percent over a span of three months. This is no mean feat as Gmail was languishing at position No. 8 in November but then leapfrogged Yahoo! Mail, (aka Hotmail), Apple Mail and in the month of January, the venerable Google Android client to claim the No. 4 position on the list.

Only 30 Percent of Opens Tracked Due to Image Blocking?

Coincidently it was during that period when Gmail turned off image blocking. Instead of having images disabled when an email is first opened, and having the user selectively turn on images, Gmail started to display images by default. Since "open tracking" requires that images on an email be displayed, when users opened an email without having images displayed, the open wasn't counted. Now that images on Gmail are automatically displayed, every single open would be tracked.

Email marketers have known of the email open number discrepancies between email clients that automatically display images (such as the iPhone Mail client) and those that don't - the other webmail clients and Microsoft Outlook. Campaign Monitor has a list of the default image blocking behaviors. However, it was never clear how large that discrepancy was.

If the boost in Gmail's numbers can be attributed completely to the automatic display of images, then it appears that email tracking was only able to track about 30 percent of the opens - or that recipients neglected to turn images on in 70 percent of the emails they were opening! This sounds like a very high number especially since commercial email tends to be image heavy and users won't be able to see much if images are turned off.

Other Possible Causes

When Gmail made the change to display images by default, they also started caching images. When a recipient opened an email, Gmail's servers would first fetch the image from the email service provider's server, store it and then serve the image to the recipient's browser. If a user were to open the same email a short time later, the image would be served by Gmail's servers.

However, what would happen if Gmail started pre-fetching images of emails that haven't been opened? This would most certainly cause a spike in recorded opens. Gmail could argue that it would provide a better experience for its users to the chagrin of the hard working email marketing analysts trying to gauge the performance of their emails.

Another item of interest is that the increase was spread over a 3 month period. Was Google rolling out its changes in stages?

Recalculating Email Client Market-Share Numbers

Since Gmail increased the email opens tracked by 270 percent, we could theoretically apply the same increases to rest of the email clients which block images by default and extrapolate their "true" market share.

Below is what is currently being reported by Litmus, as well as the recalculated market share based on a 270 percent increase. As you can see Microsoft Outlook would not only be the dominant email client, Microsoft would also hold two of the top three spots with jumping to No. 3.

What Does this Mean?

Does it mean open tracking is inherently flawed? I don't think so. Open tracking can be immensely useful to track email campaign trends as they provide a great barometer of interest from the user. In fact Litmus' Email Analytics capability go way beyond just tracking opens, they also track where emails are opened and how long the emails are being read - which helps you figure out how engaged users are with your content.

There's probably a lot going behind the scenes with Gmail's bump in numbers and we might see more theories and explanations as the months go by.

However as we've seen here, accurate email client market share numbers will probably continue to be a mystery and we should take a little bit of salt when reading reports claiming that X number of emails are being read on Y email client.

Justin Khoo is president of Advenix. He also writes a blog that covers interactive email tips and techniques at


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Terms: Feel free to be as big a jerk as you want, but don't attack anyone other than me personally. And don't criticize people or companies other than me anonymously. Got something crappy to say? Say it under your real name. Anonymous potshots and personal attacks aimed at me, however, are fine.

Posted by: Steve B
Date: 2014-03-07 15:08:41
Subject: attrition

I imagine that gmail received a boost in users due to Yahoo's outage earlier this year as well... not that Yahoo would admit such a thing...
Posted by: robinteractive
Date: 2014-03-04 16:28:13
Subject: Google Apps?

"Another item of interest is that the increase was spread over a 3 month period. Was Google rolling out its changes in stages?" If memory serves me right, there was a 2-3 week difference between images enabled by default in my personal Gmail account and my Google Apps-powered employer account. Either that was a staggered rollout on the part of Google, or Google Apps admins had some discretion in terms of when the feature was enabled. Official Google blogs might provide some insight.