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Microsoft Outlook alternatives: 6 apps ranked by verified data

Facts checked Oct 25, 2026AppBreakup editorialHow we rank

Common reasons people leave Microsoft Outlook: classic and new Outlook for Windows differ, which confuses users, and busy interface with many features most people never use. We ranked 6 alternatives by how directly each one replaces Microsoft Outlook, then by reviews, real visits and how recently each app's facts were checked against its own website. Gmail currently ranks first.

Quick comparison

#AppPricingOpen sourcePlatformsVerified factsScore
1Thunderbird logoThunderbirdOpen sourceYesWindows, macOS, Linux +15 of 559.6
2Proton Mail logoProton MailFree plan + paidYesWeb, Windows, macOS +35 of 553.6
  1. Thunderbird logo

    1. ThunderbirdTop pick

    Best for: Desktop users who want a free, private, customisable mail and calendar app

    Open sourceWindows, macOS, Linux, Android

    59.6

    score / 100

    Why switch from Microsoft Outlook

    Free, open-source desktop mail and calendar app with no ads or Microsoft account needed.

    Pros

    • Free, open source and funded by donations, with no ads
    • Built-in OpenPGP, calendar, filters and many add-ons
    • Runs on Windows, Mac, Linux and Android

    Cons

    • No web version and no released iOS app yet
    • Add-ons sometimes break after major updates
    • Exchange setups can need extra configuration
    Visit Thunderbird Details and reviews
    How this score is calculated
    Editorial fit ×0.377
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.1585
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Thunderbird a good Microsoft Outlook alternative?

    Verified facts

    5 of 5 verified
    Desktop platforms
    Windows, Linux, macOS
    Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
    Price
    Free, funded by donations
    Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
    Mobile app
    Open-source Android app
    Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
    Android app origin
    Formerly K-9 Mail
    Checked Oct 25, 2026github.com(opens source in a new tab)
    Android app license
    Apache-2.0
    Checked Oct 25, 2026github.com(opens source in a new tab)
  2. Proton Mail logo

    2. Proton Mail

    Best for: Privacy-minded people and teams who want encrypted email without running servers

    Free plan + paidOpen sourceWeb, Windows, macOS, Linux, iOS, Android

    53.6

    score / 100

    Why switch from Microsoft Outlook

    Encrypted email for people leaving Microsoft over privacy concerns.

    Pros

    • End-to-end and zero-access encryption by default
    • Open-source, audited apps on every major platform
    • Bundles with Proton VPN, Drive, Calendar and Pass

    Cons

    • Free plan has little storage and one address
    • Search and third-party integrations are more limited than Gmail
    • Using desktop clients needs the paid Bridge app
    Visit Proton Mail Details and reviews
    How this score is calculated
    Editorial fit ×0.357
    Reviews ×0.363
    Clicks (90 days) ×0.150
    Freshness ×0.1585
    Votes ×0.150

    0 counted reviews, 0 up and 0 down votes. Full formula

    Is Proton Mail a good Microsoft Outlook alternative?

    Verified facts

    5 of 5 verified
    Free plan
    Yes
    Checked Oct 25, 2026proton.me(opens source in a new tab)
    Mail Plus price
    $4.99/month, or $3.99/month billed yearly
    Checked Oct 25, 2026proton.me(opens source in a new tab)
    Jurisdiction
    Switzerland
    Checked Oct 25, 2026proton.me(opens source in a new tab)
    Open source
    Yes, independently audited
    Checked Oct 25, 2026proton.me(opens source in a new tab)
    License (web clients)
    GPL-3.0
    Checked Oct 25, 2026github.com(opens source in a new tab)

The best Microsoft Outlook alternative for…

The highest-ranked app in this list for each need.

Gmail logo

Best Microsoft Outlook alternative for most people

Gmail

The main free alternative, simpler to use and tightly linked to Google's apps.

Thunderbird logo

Best Microsoft Outlook alternative for a free option

Thunderbird

Free, open-source desktop mail and calendar app with no ads or Microsoft account needed.

eM Client logo

Best Microsoft Outlook alternative for a free plan you can upgrade

eM Client

A desktop client for Windows and Mac with Exchange support and a cleaner interface.

Proton Mail logo

Best Microsoft Outlook alternative for open source

Proton Mail

Encrypted email for people leaving Microsoft over privacy concerns.

Spark logo

Best Microsoft Outlook alternative for Mac

Spark

A cross-platform client that keeps Outlook accounts but adds a smarter inbox and team features.

Superhuman Mail logo

Best Microsoft Outlook alternative for Windows

Superhuman Mail

A fast, keyboard-driven client that works on top of Outlook and Microsoft 365 accounts.

Thunderbird logo

Best Microsoft Outlook alternative for Linux

Thunderbird

Free, open-source desktop mail and calendar app with no ads or Microsoft account needed.

Gmail logo

Best Microsoft Outlook alternative for iPhone and Android

Gmail

The main free alternative, simpler to use and tightly linked to Google's apps.

Gmail logo

Best Microsoft Outlook alternative for working in the browser

Gmail

The main free alternative, simpler to use and tightly linked to Google's apps.

Microsoft Outlook alternatives: common questions

What is the best alternative to Microsoft Outlook?

Gmail ranks first right now. The main free alternative, simpler to use and tightly linked to Google's apps. eM Client and Thunderbird follow it in our ranking.

Is there a free alternative to Microsoft Outlook?

Yes. Gmail (free plan + paid), eM Client (free plan + paid), Thunderbird (open source) and Spark (free plan + paid) have a free option. Check each app's verified facts for current plan limits.

Is there an open-source alternative to Microsoft Outlook?

Yes: Thunderbird and Proton Mail.

Which Microsoft Outlook alternatives work on Linux?

Thunderbird and Proton Mail run on Linux.

Why do people switch from Microsoft Outlook?

The complaints we hear most: classic and new Outlook for Windows differ, which confuses users; busy interface with many features most people never use; free accounts show ads and get less storage.

How is this list ranked?

Every app is scored with the same published formula: how directly it replaces Microsoft Outlook, reviews (weighted by verification), visits from AppBreakup, how recently its facts were checked against its own website, and reader votes.