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Open source Microsoft Outlook alternatives

Top Email Clients & Providers like Microsoft Outlook

The most popular alternative to Microsoft Outlook is Thunderbird, which has a free version. Other great alternatives to Microsoft Outlook are Proton Mail and Mailspring.

Most alternatives to Microsoft Outlook are in the Email Clients & Providers category, compared here by price, platform and features.

Microsoft Outlook alternatives
AllFreeOpen source
3 apps

All Microsoft Outlook alternatives

  1. Thunderbird

    Thunderbird is a free and open-source email client for Windows, macOS and Linux, with an Android app based on K-9 Mail. It manages multiple accounts in a unified inbox and includes a calendar, address book, chat and built-in OpenPGP encryption. Add-ons and themes customize it extensively, and it is developed by MZLA Technologies, a Mozilla Foundation subsidiary funded by user donations.

    9 Thunderbird alternatives

    Pros

    • Free and open source, funded by donations rather than ads
    • Built-in OpenPGP encryption, calendar and address book
    • Highly customizable with add-ons and themes

    Cons

    • Interface feels busier than minimalist modern clients
    • Getting the most out of it takes some setup and add-ons
    Cost / License
    FreeOpen source
    Categories
    Email Clients & Providers
    Platforms
    WindowsMacLinuxAndroid
    Features
    Ad-freeCalendar viewEnd-to-end encryptionOffline modePlugins & extensionsUnified inbox
    Visit websiteMore about Thunderbird

  2. Proton Mail

    4.8(48.7K) · App Store

    Proton Mail is an end-to-end encrypted email service based in Switzerland. Messages between Proton users are encrypted automatically, emails to others can be password-protected, and stored mail uses zero-access encryption so Proton cannot read it. Its apps are open source, paid plans add custom domains and more addresses, and it is part of a suite with Proton Calendar, Drive, VPN and Pass.

    9 Proton Mail alternatives

    Pros

    • End-to-end and zero-access encryption protect stored mail
    • Based in Switzerland, with open source apps
    • Part of a suite with Proton Calendar, Drive, VPN and Pass

    Cons

    • Free plan is tight on storage and addresses
    • Using IMAP clients requires Proton Mail Bridge and a paid plan
    Cost / License
    FreemiumOpen source
    Categories
    Email Clients & Providers
    Platforms
    WebWindowsMacLinuxiPhoneAndroid
    Features
    Custom email domainEmail aliasesEnd-to-end encryptionSend laterTracker blockingTwo-factor authentication
    Visit websiteMore about Proton Mail

  3. Mailspring

    17.9Kstars

    Mailspring is a free, open-source desktop email client for Windows, macOS and Linux that works with Gmail, Office 365, iCloud and any IMAP account. It offers a unified inbox, fast search, themes and templates, and runs its mail sync engine locally rather than in the cloud. An optional Pro subscription adds read receipts, link tracking, send later and reminders.

    7 Mailspring alternatives

    Pros

    • Free and open source on Windows, Mac and Linux
    • Sync engine runs locally rather than through a cloud service
    • Unified inbox, themes and templates in a clean interface

    Cons

    • Send later, reminders and read receipts require Pro
    • A Mailspring ID account is required even for the free version
    • No mobile apps to go with the desktop client
    Cost / License
    FreemiumOpen source
    Categories
    Email Clients & Providers
    Platforms
    WindowsMacLinux
    Features
    Dark modeEmail trackingSend laterTemplatesUnified inbox
    Visit websiteMore about Mailspring

Microsoft Outlook vs its alternatives at a glance

Pricing, platforms and the key features of Microsoft Outlook, compared with its most popular alternatives.

Microsoft Outlook vs its alternatives at a glance
AppPricingPlatformsAI assistantCalendar viewIntegrationsOffline modeSend later
Microsoft OutlookFreemiumWeb, Windows, Mac, iPhone, Android
ThunderbirdFreeOpen sourceWindows, Mac, Linux, Android
Proton MailFreemiumOpen sourceWeb, Windows, Mac, Linux, iPhone, Android
MailspringFreemiumOpen sourceWindows, Mac, Linux

Microsoft Outlook alternatives: frequently asked questions

What is the best alternative to Microsoft Outlook?

The most popular alternative to Microsoft Outlook is Thunderbird: Free, open-source desktop email client from Mozilla. Other great alternatives are Proton Mail and Mailspring.

Is there a free alternative to Microsoft Outlook?

Yes, 3 alternatives are free or have a free plan, including Thunderbird, Proton Mail, and Mailspring.

Is there an open source alternative to Microsoft Outlook?

Yes, 3 open source alternatives are listed, including Thunderbird, Proton Mail, and Mailspring.

Is Microsoft Outlook free?

Microsoft Outlook has a free plan, with paid plans that unlock more features.

Compare Microsoft Outlook with its alternatives

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