Sustainable Substitutes for Outlook

A wide-spread email client owned by Microsoft.

outlook logo

Reasons to avoid Outlook

Microsoft Outlook should be avoided because it is a data-harvesting and advertising channel that transmits sensitive credentials to Microsoft servers, shares user data with hundreds of advertising partners and imposes AI features that users cannot properly disable. Microsoft is known for its tax avoidance schemes and support of Donald Trump.

Please choose a more ethical and sustainable alternative.

Ethical and Sustainable Outlook Alternatives

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  • Feasibility: How easily can the average user switch to this substitute? Higher feasibility results in a higher ranking.
  • Editor's Rating: How sustainable is the substitute? The more sustainability attributes it fulfils, the higher it is ranked.
fairemail logo

FairEmail

Fully featured, privacy oriented email client for Android

FairEmail is developed by FairCode B.V., the company of Dutch developer Marcel Bokhorst.
airEmail displays no advertisements, and it contains no analytics and no tracking of any kind, as the developer states explicitly on the project website.
FairEmail is open-source and licensed under GPL-3.0, with the full source code published on GitHub, which permits independent audits and community contributions.
The app blocks tracking pixels, confirms the loading of images and links to prevent tracking, strips unsafe HTML, stores no data on third-party servers and sends no data to the developer except opt-in error reports.
No account with the developer is required, because FairEmail is a client only; you bring your own email address and the app requires no sign-up beyond your existing mailbox credentials.
Almost all features can be used free of charge, with advanced functions such as filter rules, S/MIME support and scheduled sending unlocked through a single one-time in-app purchase rather than a subscription.
FairEmail offers offline storage and offline operations, so messages can be read, searched and composed without an internet connection.
FairEmail is deliberately battery friendly, frugal with data and small at under 30 MB, which reduces both energy and resource consumption compared with the considerably heavier email applications of large providers.
Website
thunderbird logo

Thunderbird

An open-source email and productivity app by Mozilla.

Thunderbird displays no advertisements and does not engage in data mining, as the project states explicitly on its website.
Thunderbird is free and open-source software licensed under the Mozilla Public License 2.0, which allows anyone to inspect, modify and share the code.
Thunderbird stores all data locally on the user's device, does not collect personal data unless the user asks it to, promises never to sell data and includes built-in OpenPGP encryption.
No account with the developer is required, because Thunderbird is a client that connects to the user's existing email accounts, and nothing is gated behind a sign-up.
Thunderbird is free forever and funded primarily by user donations, with the announcement that features deliverable on the user's own device will never be placed behind a paywall.
Thunderbird is highly extensible through its large add-on ecosystem and themes, which allow users to add functionality such as enhanced filtering, additional encryption tools and visual customisation.
As a client that fetches messages to the user's own device, Thunderbird provides full offline access to mail, calendars and contacts without a browser or an internet connection.
Website

The 8 main issues with Outlook

Big Tech - Big Tech companies do not nourish people and planet. This is especially true in times of political tension.

Outlook is a cornerstone product of Microsoft, one of the largest technology corporations in the world. The new Outlook replaces the bundled Windows Mail application and Microsoft is retiring the classic client with its local data processing in order to redirect all customers to its own cloud, which deepens dependence on the Microsoft ecosystem. Source: heise online: New Outlook: Microsoft spares companies another year (2026)

Privacy Concerns - User data is likely to be stored and used against users' best interest.

The new Outlook transmits email login credentials, including IMAP and SMTP passwords of third-party accounts, to Microsoft servers in the United States. In addition, a Copilot bug allowed the AI assistant to bypass privacy blocks and read confidential Outlook emails. Source: heise online: Microsoft lays hands on login data: Beware of the new Outlook (2023)PCWorld: Microsoft is halting forced installs of Microsoft 365 Copilot app (2026)

Lack of Transparency - Opacity in operations, data handling, or supply chains, making it difficult for users to understand practices.

The disclosure about data sharing with 772 partners is shown only in the EU, where the GDPR compels Microsoft to reveal it; users elsewhere are not informed. Similarly, Copilot features in Outlook ship without a genuine off switch, leaving licence downgrades as the only reliable escape. Source: Thurrott.com: New Outlook Decried as a Surveillance Tool for Targeted Advertising (2024)Office Watch: Outlook Copilot Search Updates and Future Plans (2026)

AI Bloat - Service has unnecessary or harmful AI features.

Microsoft is embedding Copilot into every corner of Outlook: the sidebar, the ribbon, the compose box and the search bar. The Copilot Search feature placed AI results above users' actual emails without an option to disable it and was withdrawn only after months of backlash. A floating Copilot button was forced onto the interface until user outrage led to its partial removal and Copilot is now being pushed into the classic desktop client as well. Microsoft also halted forced installs of the Microsoft 365 Copilot app following heavy criticism. Source: Office Watch: Outlook Copilot Search Updates and Future Plans (2026)The Register: Microsoft lets users exile floating Copilot button after interface rage (2026) The Register: Microsoft makes Copilot harder to miss in Classic Outlook (2026)PCWorld: Microsoft is halting forced installs of Microsoft 365 Copilot app (2026)

Monopoly - Market dominance that stifles competition and limits user choice.

Italy's competition authority AGCM has opened an antitrust investigation into Microsoft over the automatic installation of Microsoft 365 Copilot on enterprise personal computers, examining how Microsoft leverages its dominant productivity-suite position to force AI products onto customers. Source: TechTimes: Microsoft 365 Copilot Auto-Installs on Enterprise PCs: Italy Launches Antitrust Probe (2026)

Tax Avoidance - Aggressive strategies are being deployed to avoid paying taxes.

The United States IRS determined that Microsoft owes 29 billion dollars in back taxes covering 2004 to 2013 after an investigation into a profit-shifting arrangement in Puerto Rico. A federal judge found that a significant purpose, if not the sole purpose, of Microsoft's transactions was to avoid or evade federal income tax. Source: ProPublica: How a Maneuver in Puerto Rico Led to a $29 Billion Tax Bill for Microsoft (2023)

Greenwashing - Misleading consumers about the environmental impact or sustainability of products or services.

Microsoft uses RECs to claim its data centers are 100% renewable, but its reliance on grids that still burn fossil fuels and its partnerships with oil and gas companies (e.g., Chevron) undermine these claims.Source:Wired: Amazon, Google, Microsoft: Here's Who Has the Greenest Cloud (2019)

Support of Authoritarian Regimes - Companies actively supporting, financing and legitimising regimes and unethical policies.

Microsoft is financing Donald Trumps plans to create a new ballroom in the white house, hoping to benefit from upcoming laws. Microsoft CEO Satya Nadella donated $1 Million to Trumps inauguration fund.Sources: OpenSecrets: Trump ballroom donors poised to benefit from AI plan they helped shape (2026)The Verge: Tech’s shift to Trump: all the companies and execs kissing the ring (2025)

Suggestions and Feedback

If you have suggestions for more alternatives or general feedback, please contact me via email or create an issue over on Codeberg. Suggest Substitute on Codeberg Write an Email