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Email Client Market Share in May 2021: The Recovery of Mobile and More

Small shifts over time lead to big change—and email client market share is no exception to that! That’s why, in our new blog series, we’re taking a closer look at the changes happening with email client market share every month. And we’ll keep you up to speed on the latest insights.

When we looked back at the first quarter of 2021, our key takeaways were Apple iPhone’s continued stronghold as the most popular email client and the changes that took place with Google Android, Outlook Mobile, and Windows Live Mail. But what highlights took place last month?

Let’s see how email client market share changed in May 2021.

Top 10 email clients overall


The top 3 email clients are still Apple iPhone, Gmail, and Apple Mail. And although their ranking is the same, there have been some interesting shifts.

Apple iPhone continues to rank as the top email client overall, further securing its spot as number one. From March to May, Apple iPhone’s share of opens has increased by 19%—from 38.9% to 47.1%. Additionally, Apple Mail gained market share, increasing by 12%, from 11.5% in March to 13% in May.

Note: A misreporting occurred with Litmus Email Analytics on Gmail from May 10th to June 7th, 2021 which may have caused a lowered reported number of opens for this period.

Among these top 3 players, things are looking up for Apple iPhone and Apple Mail. Where will Gmail be next month?

  1. Apple iPhone: 47.1%
  2. Gmail: 18.6%
  3. Apple Mail: 13%
  4. Outlook: 9.0%
  5. Yahoo! Mail: 5.7%
  6. Google Android: 2.3%
  7. Apple iPad: 1.6%
  8. 1.2%
  9. Samsung Mail: 1.0%
  10. Windows Live Mail: 0.2%

Outside of the top clients: Outlook, Yahoo! Mail, Google Android, and Apple iPad have all gained market share slightly, but kept their previous ranking. Samsung Mail and swapped spots back in April and are holding on to their new positions, with Windows Live Mail following behind the two.

In particular, Outlook Mobile and Windows Live Mail piqued our interest at the end of March, with Outlook Mobile at 10th place and Windows Live Mail at 11th. Now, Windows Live Mail has climbed up to 10th place, with Outlook Mobile dropping all the way back to 13th place at 0.1% market share.

Opens by environment


Since its decline in the middle of 2020, mobile continues to ramp back up, increasing its share by nearly 16% from March. It has even surpassed its share from before the onset of the COVID-19 pandemic, from 42% in 2019 to 49.7% in May 2021 (an 18.3% increase). Could this be an emerging “new normal” for mobile environments?

With mobile’s increase, webmail and desktop have lowered in popularity. Our speculation is that it’s due to some sense of social and economic normalcy, with the reopening of businesses that were affected by the COVID-19 pandemic.

  1. Mobile: 49.7%
  2. Webmail: 27.5%
  3. Desktop: 21.2%
  4. Other: 1.7%

Most popular mobile opens


  1. Apple iPhone: 90.5%
  2. Google Android: 4.4%
  3. Apple iPad: 3.0%

Apple iPhone continues to take the lead in mobile email with a 90.5% share. Google Android sits at number two, the same ranking it had in March. Apple iPad has dropped slightly as well, nearly 7%.

Most popular webmail clients


Although webmail overall has lowered in popularity, Gmail still holds a solid grip as the most popular webmail choice, with 72.1% of webmail market share.

  1. Gmail: 72.1%
  2. Yahoo! Mail: 22.2%
  3. 4.8%

Most popular desktop clients

desktopclientsApple Mail continues to be the most popular desktop client at 58.4% of desktop client market share—however, it decreased slightly in popularity from March to May by 0.9%. Not too far off is Outlook, which has increased a little by 1.3%, from 40% to 40.5%. Windows Live Mail has stayed the same in third place.

  1. Apple Mail: 58.4%
  2. Outlook: 40.5%
  3. Windows Live Mail: 0.9%

What will happen next?

Overall, the key insight we’re seeing for May is mobile coming back strong after its fallout in the middle of 2020. Will this trend continue, and if so, how will that affect webmail and desktop in the long run? Stay tuned as we report back next month.

Where did we get all this data? Our email client market share stats are pulled from billions of opens, anonymously collected and aggregated with Litmus Email Analytics from May 1-31, 2021. It highlights global trends across all industries and verticals. Some email clients may be over- or under-represented due to image blocking.

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Originally published June 8, 2021. Last updated June 14, 2021.

Kimberly Huang

Kimberly Huang

Kimberly Huang is a Content Marketing Manager at Litmus