A List of Email Client User Agents (Plus Our Most Popular Client)

A few years ago when we built our custom newsletter system for Detailed Image I wrote about all of the extensive features it included. One feature we overlooked though was user agent tracking for opens, which can be used to determine which client the subscriber is using to open and read the email.

Lacking this information became a problem when we went responsive with all of our newsletters last year and had to determine how to prioritize our client testing. We wanted it to be data-driven just like our browser testing. What we did at the time was look at the distribution of email addresses by service (i.e. Gmail, Yahoo, AOL), look at the devices/browsers being used on our website, and then use that info to make an educated guess. Of course, I also updated our open tracking to start tracking user agents so we could have this information in the future.

The iPhone Rules For Us

Last week we launched a redesigned Daily Special newsletter. During the development process I dug into this data a bit so that we could finally come up with the most efficient testing process. I was shocked to find that roughly 1/3 of all newsletters are opened on in Apple Mail on an iPhone! Turns out that the info we were using previously to estimate email client usage was way off. Just because someone has a Gmail account, doesn’t mean they’re using Gmail to read their emails. I knew that this was happening, but didn’t realize the prevalence. It goes to show the power of defaults. Why download the Gmail app when the default Mail app does the job?

Email Client User Agents

In the process of analyzing our data, I wasn’t able to find a good list of email client user agents so I decided to make my own. I opened my newsletter in every client I had accessible to me and then noted the user agents. The list is below, hopefully it saves someone else some time. Please note, this is from March of 2015 so as time goes on it may not be as accurate.

Gmail on the Web

mozilla/5.0 (windows nt 5.1; rv:11.0) gecko firefox/11.0 (via ggpht.com googleimageproxy)

Gmail App on Android Lollipop

mozilla/5.0 (windows nt 5.1; rv:11.0) gecko firefox/11.0 (via ggpht.com googleimageproxy)

Android Email on Lollipop

mozilla/5.0 (linux; android 5.0; sm-n900t build/lrx21v) applewebkit/537.36 (khtml, like gecko) version/4.0 chrome/ mobile safari/537.36

iPhone on iOS 8

mozilla/5.0 (iphone; cpu iphone os 8_1 like mac os x) applewebkit/600.1.4 (khtml, like gecko) mobile/12b411

iPad on iOS 8

mozilla/5.0 (ipad; cpu os 8_2 like mac os x) applewebkit/600.1.4 (khtml, like gecko) mobile/12d508

Outlook 2013 on Windows 8.1

mozilla/4.0 (compatible; msie 7.0; windows nt 6.2; wow64; trident/7.0; .net4.0e; .net4.0c; .net clr 3.5.30729; .net clr 2.0.50727; .net clr 3.0.30729; bri/2; asu2js; microsoft outlook 15.0.4701; ms-office; msoffice 15)

Thunderbird on Windows 8.1

mozilla/5.0 (windows nt 6.3; wow64; rv:24.0) gecko/20100101 thunderbird/24.4.0

The first thing you might notice is that Gmail on the web has the same user agent as Gmail on Android (and it’s also the same on iOS). The reason is that Gmail caches all images on their server so when a user downloads our 1 x 1 pixel it’s coming from the “googleimageproxy” and not our server. Lame, but not a whole lot you can do about it.

This covers what was most popular for us, and thus what we were most interested in learning. If I’m missing any popular clients that you know a user agent for, let me know in the comments and I’ll add them.

Tallying Up User Agent Data

Armed with the user agents above it’s not too hard to quickly get a breakdown of email client usage with some simple pattern matching. This can be done with a regular expression in any programming language or with a spreadsheet. I chose the spreadsheet route. I exported our data and then used the following formulas to get a tally, where “range” is the range of cells where your raw data is located:


=COUNTIF(range, "*googleimageproxy*")

Android Email

=COUNTIF(range, "*android*")


=COUNTIF(range, "*iphone*")


=COUNTIF(range, "*ipad*")


=COUNTIF(range, "*outlook*")


=COUNTIF(range, "*thunderbird*")

3 comments on A List of Email Client User Agents (Plus Our Most Popular Client)

  1. Tim says:

    Not too surprised about the 1/3 of opens coming from iPhone, another iOS’ism I’ve seen is that they are more “valuable” visitors. Higher AOV, much higher conversion rate (in particular on iPad), more time spent on the site, more pages visited, etc… Just across the board much higher value to the top and bottom lines. Conversely Android devices are exactly opposite, much lower conversion rates, much lower AOV, lower time spent on the site and lower engagement.

    While none of this is too surprising the biggest surprise to me, is the totally unthinkable. In terms of revenue, we see really unusual stuff (largely due to the price of the products the company I work for sells) , for example YTD, the Amazon Fire Phone is the #4 revenue driver, odder yet, the Barnes and Noble Nook HD tablet is #6 – all ahead of any branded Android device!

    As challenging as this is to plan for, I’ll still take it any day of the week over the mess IE6, IE7 and even IE8 cause!

    Thanks for sharing Adam!

    • Adam McFarland says:

      Thanks for sharing Tim.

      For us, Android is actually pretty good. It’s not quite iOS in terms of total visits or revenue, but conversion rate is only slightly lower and AOV is actually slightly higher. Overall they’re both really good customer bases for us, but we may be an exception to the rule because I’ve heard a lot of stories like yours where Android visitors aren’t good customers.

      I’m and Android guy and I spend quite a bit on my phone so we’re definitely out there, but there’s also a lot of Android customers on low-end phones who don’t spend any $. You almost have to segment Android by premium phones vs. low-end to get a better comparison since all iOS phones are premium phones.

      And yes, much better than the days of IE hell 🙂

      (although we still support IE8 since it’s the last version on XP and we still have a decent amount of people using it…we check the stats every quarter or so, can’t wait until usage is low enough for us to drop it!)

      – Adam

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