Brandwave

Proton Mail vs Thunderbird:Which is more popular?

In September 2026, Thunderbird had more branded searches than Proton Mail among email clients worldwide. Thunderbird had about 29,100 branded searches, while Proton Mail had 320. Thunderbird made up 25.9% of all email client searches we track, and Proton Mail accounted for 0.28%. When we asked ChatGPT and Google AI Overviews about email clients, Thunderbird appeared in four of the five answers and Proton Mail in three. Thunderbird was mentioned before Proton Mail in three out of five answers.

Among email clients worldwide in September 2026

Who do people search for more?

Thunderbird, about 91 searches for every 1 for Proton Mail

Thunderbird 29.1K searchesProton Mail 320 searches

Who does AI mention more?

Thunderbird, mentioned in 4 of 5 answers, Proton Mail in 3

Thunderbird in 4 of 5Proton Mail in 3 of 5

Who does AI recommend more?

Thunderbird, named ahead of Proton Mail in 3 of 5 answers

Thunderbird first in 3Proton Mail first in 2

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Top email clients in ChatGPT and Google AI Overviews

In three ChatGPT questions and two Google AI Overviews, Thunderbird was mentioned in four out of five: in all three ChatGPT answers and in one of the two Google AI Overviews. Proton Mail was mentioned in three out of five: in two of the three ChatGPT answers and in one of the two Google AI Overviews. Thunderbird was listed before Proton Mail in three out of five answers.

Most recommended by AI

Brands get a higher ranking if they are mentioned earlier in the answers.

  1. Spark1st
  2. Thunderbird2nd
  3. Proton Mail3rd
  4. Superhuman4th
  5. Airmail–
  6. Newton–

Mentioned by AI

Each dot is one answer, filled in when that answer mentions the brand.

  • Spark4 of 5Named in 2 of 3 ChatGPT answersNamed in 2 of 2 Google answers
  • Thunderbird4 of 5Named in 3 of 3 ChatGPT answersNamed in 1 of 2 Google answers
  • Superhuman3 of 5Named in 2 of 3 ChatGPT answersNamed in 1 of 2 Google answers
  • Proton Mail3 of 5Named in 2 of 3 ChatGPT answersNamed in 1 of 2 Google answers
  • Airmail0 of 5Named in 0 of 3 ChatGPT answersNamed in 0 of 2 Google answers
  • Newton0 of 5Named in 0 of 3 ChatGPT answersNamed in 0 of 2 Google answers

See every answer about email clients

5 answers

Not named in any answer:

Brands are shown in the order each answer named them. The survey took place in the United States on October 20, 2026.

Is Proton Mail or Thunderbird more popular in search?

This chart shows how often people search Google for Proton Mail and Thunderbird by name. Each line represents a brand's share of searches for all six email clients we track, month by month, from English-language searches worldwide.

Proton Mail and Thunderbird among email clients worldwide, by month

Share of searches by month for Thunderbird, Proton Mail. The figures are in the table below the chart.

View monthly share of searches table
MonthSparkThunderbirdSuperhumanAirmailNewtonProton Mail
Oct 202523.5%36.1%20.2%19.3%0.76%0.12%
Nov 202521.6%34.5%25.1%17.7%0.97%0.14%
Dec 202520.2%34%23.8%20.3%1.5%0.13%
Jan 202618.6%38.3%26.8%15.3%0.84%0.14%
Feb 202614.6%39%33.3%12%0.99%0.17%
Mar 202615.6%36.5%34.1%12.8%0.76%0.18%
Apr 202615.6%36.5%33.5%12.8%1.4%0.15%
May 202616.8%34.7%36.4%11.3%0.67%0.16%
Jun 202621.4%29.6%27.7%17.6%3.5%0.2%
Jul 202620.7%35%29.1%13.9%1.1%0.24%
Aug 202622%35.2%23.7%18.1%0.71%0.26%
Sep 202636%25.9%24%13.2%0.64%0.28%

How has the Proton Mail and Thunderbird comparison changed over the last 12 months?

3 findings
  • Thunderbird was ahead of Proton Mail in every measured month of the 12 months ending September 2026.
  • Across the 12 months ending September 2026, Proton Mail’s share of searches among email clients worldwide moved from 0.12% to 0.28%, and its estimated monthly branded searches moved from 140 to 320.
  • Across the 12 months ending September 2026, Thunderbird’s share of searches among email clients worldwide moved from 36.1% to 25.9%, and its estimated monthly branded searches moved from 41.6K to 29.1K.

How did search popularity change for email clients worldwide in September 2026?

3 changes

  1. In September 2026, Spark overtook Thunderbird and Superhuman to become the leader among email clients worldwide, with 36% of the searches.

  2. In September 2026, Thunderbird lost share of searches among email clients worldwide, from 35.2% to 25.9%.

  3. Estimated monthly branded searches for Proton Mail worldwide rose 128.6% over 12 measured months, from 140 to 320 in September 2026.

How are branded searches counted?

4 search terms

Brandwave collects information about searches that people make online using Proton Mail’s and Thunderbird’s names. When viewed over time, estimated search volumes for these branded terms can be used to understand whether interest in the brands is growing, holding steady, or fading.

Proton Mail

1 branded search term

  • email proton mail

Thunderbird

3 branded search terms

  • thunderbird client
  • thunderbird email
  • thunderbird email client

How the Brand Demand Index is measured

Other head-to-heads among email clients

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