The complex world of email open rates

iOS, Android, and the effect on the Open Rate

With more and more emails read on mobile devices, things are getting trickier when it comes to calculating the open rate for your email campaigns. Take this sender: around 28% of messages are read on a mobile device, of which 78.5% are iOS devices (iPhones and iPads). Will that affect their Open Rate? Yes. Let’s see why.

Consider this:

• Whether an email has been opened is typically tracked by determining whether an image has been downloaded
• On iOS (iPhone/iPad) images are downloaded by default
• On Android (default email client and Gmail) images are blocked by default
• On most desktop and Web clients, images are blocked by default

Let’s focus on mobile readers. The above means that the same recipient, speed-browsing through his or her emails:

• On an iPhone is counted as an opener, regardless of whether she decides to actually read the message
• On a Samsung Galary is not counted as an opener, unless he decides to download images while reading the message

Which – in terms of the open rate – translates into the following:

• The more iOS recipients you have, the higher the risk of overestimating the open rate
• The more Android recipients you have, the higher the risk of underestimating the open rate
• The higher the percentage of mobile users, and the higher the percentage of those on iOS devices, the higher the open rate

So that little number that you see in your email stats summary is a bit trickier to interpret than it used to be. Let’s keep going.

Click Rates are not affected by mobile, but Click-to-Open Rates are

The Click Rate (unique and total) is not affected by the above, thank goodness! Whether you are on a mobile device or not, either you click or you don’t.

However, if you like keeping an eye on the Click-To-Open Rate (CTOR = did they click after opening? How effective was my message?), be careful: the open rate appears in that formula, and therefore the increase in mobile readers could affect the CTOR, pushing it down as the number of opens increases.

If you’ve seen an increase in the Open Rate and a decrease in the CTOR over the last 12 months, for example, now you know why!

This – by the way – is exactly what Epsilon found in their Q2 2013 report. The report shows the Open Rate growing 28% over the last two years: from 22.2% in Q2 2011 to 28.5% in Q2 2013 (as shown in the chart below). The CTOR instead (not shown in the chart below) decreased pretty sharply over the same time period from 23.4% to 15.08%

What about readers that don’t download images?

I’m one of them: I often read emails on my Android phone without downloading images, feeling bad for messing up the sender’s statistics. Well, not quite. Professional email marketing systems have a way to intelligently “guess” those like me that read without downloading images.

For example, if you take a closer look at the Opens section of your campaign stats in MailUp, you will see something like this:

As you can see, there is a metric called Opens only txt. Those are readers that we are “guessing” read the message. The guess is an educated one, calculated as follows:

• We start with the assumption that the likelyhood to click is the same for those that see and those that don’t see images in the message (*)
• That means that CTOR (with images) = CTOR (without images)
• Which can be written as: UNIQUE CLICKS (with images) / UNIQUE OPENS (with images) = UNIQUE CLICKS (without images) / UNIQUE OPENS (without images)
• Since we know who clicked, this gives us the number that we are looking for: UNIQUE OPENS (without images) = (UNIQUE CLICKS (without images) * UNIQUE OPENS (with images)) / UNIQUE CLICKS (with images)

(*) Note that if you disagree with the assumption that the CTOR is the same and believe that those that see the message with images are more likely to click, that’s certainly OK. It simply means that the metric that you find in MailUp underestimates the number of opens without images (and underestimating won’t normally get in you in trouble!).

Don’t pop the champagne based on the OR

Some takeaways from the above:

1. Don’t pop the Don Perignon based on the Open Rate: an increase may not be due to killer email creatives!
2. Don’t fire your email marketing guy over a decrease in the CTOR: he’s probably not lost his touch.
3. The % of readers on a mobile device is only getting larger (we’ve seen clients of ours at 90% on some campaigns!): the distortion effect on the Open Rate is likely to increase.
4. Clicks matter: we can debate all we want about the Open Rate, but clicks are clicks. Either somebody clicked, or they didn’t, regardless of email client and image downloading behavior.
5. Since clicks are key:
   1. Try to include a call to action in all messages to properly track campaign performance.
   2. A/B test on the Click Rate (or conversion) more than the Open Rate.
   3. Lots of traffic is from mobile: landing pages should be mobile-ready.

Happy emailing!

This article was written by

Massimo Arrigoni

As head of products at MailUp, I spend my days (and nights) thinking of new tools that can help marketers get the job done more effectively. In MailUp 9, for instance, we just introduced a new way for our users to collaborate on email campaigns. With beefree.io, we took our drag-n-drop email editor and turned into a stand-alone, embeddable plugin. The objective is to create tangible value, gather feedback, and push real product innovation based on it.