Open Source Windows Email Clients
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Email Clients for Windows
View 39 business solutionsBrowse free open source Email Clients and projects for Windows below. Use the toggles on the left to filter open source Email Clients by OS, license, language, programming language, and project status.
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Windows MBox Viewer
Windows eml and mbox viewer.
Free Windows Mbox Viewer. Gain access to mbox archives, single eml or single Outlook messages. View attachments and export single mails in eml format. Access large mbox files such as Google Takeout or Mozilla Thunderbird Archives. Development of mbox viewer continues now at github: https://github.com/eneam/mboxviewer **NOTE**: Windows Defender may sometimes report incorrectly that mbox-viewer contains malware. Please report the case to the development. Development will ask Windows Security to update Windows Defender rules to resolve the issue. Last time the incorrect detection was corrected by Microsoft Security within few hours. User will need to run Windows Update to install the latest updated detection rules. -
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SquirrelMail is a PHP-based Web email client. It includes built-in pure PHP support for IMAP and SMTP, and renders all pages in pure HTML 4.0 for maximum compatibility across browsers. It has strong MIME support and a flexible plugin system.
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Outlook Mail Merge Attachment is a script which can be used to add an attachment to an mail merge in Microsoft Outlook.
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PHPMailer
A full-featured email creation and transfer class for PHP
A PHP email creation and transport class featuring file attachments, SMTP servers, CCs, BCCs, HTML messages, word wrap, and more. Sends email via sendmail, PHP mail(), QMail, or with SMTP. PHPMailer is used by many popular PHP development frameworks and is one of the most popular email-generating and sending libraries in the world. This project is defunct here on sourceforge – it's now maintained on Github at https://github.com/PHPMailer/PHPMailer. Documentation is available at https://github.com/PHPMailer/PHPMailer/wiki -
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Mailspring
A faster, leaner email client and fork of Nylas Mail
Mailspring is a fast and lean mail client that’s a new version of Nylas Mail. It’s maintained by one of Nylas Mail’s original authors, with plenty of great features and enhancements such as a new C++ sync engine that allows it to use 50% less RAM. Heavy dependencies have also been removed and the package manager rewritten for even greater speed. Written in TypeScript with Electron and React, it is cross-platform (macOS, Windows and Linux) and designed to be easy to extend. -
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Proton Mail Bridge
Proton Mail Bridge application
Proton Mail Bridge is a desktop application that runs in the background on Windows, macOS, and Linux to enable users to access their Proton Mail encrypted email accounts with traditional email clients like Outlook, Thunderbird, Apple Mail, and others via local IMAP/SMTP servers. Because standard IMAP cannot natively decrypt end-to-end encrypted messages, Bridge acts as a translator that downloads encrypted mail, decrypts it locally, and serves it to your preferred mail client over a local server, while encrypting outgoing messages before they’re sent to Proton’s servers. It provides a seamless integration layer for users who need offline support, familiar local client workflows, or tighter integration with desktop tools while preserving Proton’s zero-access encryption model. The Bridge app continues running even when its GUI is closed so that mail clients can remain connected and synchronized, and it supports automatic startup and robust credential handling via secure storage. -
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RainLoop Webmail
Simple, modern & fast web-based email client
RainLoop Webmail is a modern, fast, and lightweight web-based email client. It supports IMAP and SMTP protocols, allowing users to access and manage their email accounts through a web interface. RainLoop offers features like multi-account support, a responsive UI, and integration with popular email providers. It is self-hosted, giving users control over their email data. -
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Tutanota
Open source email service with a strong focus on security and privacy
Tutanota is an open source email client focused on security and privacy. It is built with end-to-end encryption and 2FA, so you can be assured of utmost email security. Tutanota is always encrypted, so whether you’re using their secure webmail client, mobile apps or desktop clients, you can be sure to communicate securely. -
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threadkey
Add keyboard shortcuts to switch between different thread views
Strike the 'T' key to sort messages by thread, strike the 'U' key to sort unthreaded again, just like the 'G' key switches to Grouped By Sort view. -
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PoptrayU
Email Notifier For Windows
This email notifier sits in your system tray and pops up a notification when new messages arrive. Preview your email before downloading it to your mail client or launching webmail applications. Create rules to delete or change the priority of messages. This program builds upon the open source PopTray mail notifier adding many new features including Windows Vista/7/8/10 support, UTF-8 and unicode support, HTML Preview, IMAP support, TLS & SASL support, etc. -
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HERMES Mail
The cult-favourite eMail client formerly known as Qualcomm Eudora
eMail traffic is on the rise. With over 100 man-years of development time behind it and a clean, intuitive interface that makes handling messages a breeze, Hermes Messenger (formerly known as QUALCOMM Eudora) is more than a way to send and receive mail: it's a powerful management tool with features to increase your productivity and enhance your communications. It is the best eMail program for people who get lots of it. If you're not yet one of them, you soon will be. Take control of your eMail before it takes control of you! Hermes provides industrial-strength communication, free of ads and free of cost. -
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Cypht
Lightweight Open Source webmail written in PHP and JavaScript
All your E-mail, from all your accounts, in one place. Cypht is not your father's webmail. Unless you are one of my daughters, in which case it is your father's webmail. Cypht is like a news reader, but for E-mail. Cypht does not replace your existing accounts - it combines them into one. And it's also a news reader. The driving force behind Cypht development is to provide combined views for multiple accounts, but it's also a standard E-mail client that lets you browse and manage IMAP folders and send outbound messages with SMTP. Cypht is an application built entirely of plugins, or as we call them, module sets (which is obviously way cooler sounding than plugins), that are executed by the framework. Modules provide a flexible way to add new features or customize the program without hacking the code. Cypht is Open Source (LGPL V2), and written in PHP and JavaScript. -
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PopTray is a mail notifier written in Delphi for the Windows platform. It sits in your tray notification area and check mail from multiple accounts on a timer interval. Preview, Delete, Rules, Plug-ins and translated into more than 30 languages.
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Magic Mail Monitor3 - Windows mail checker with multiple mailboxes support, ability to preview and delete messages. Based on original code of Magic Mail Monitor from Valeriy Ovechkin.
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NOCC is a simple and fast Webmail client which can handle POP3 and IMAP mailboxes and sends email via SMTP. It is written with PHP, has low requirements (no database, frames). Features multi-language support, MIME attachments, displays HTML messages. The installation guide comes with the source code: https://sourceforge.net/p/nocc/code/HEAD/tree/trunk/webmail/docs/INSTALL If you encounter problems or bugs you can always try the current HEAD version: https://sourceforge.net/p/nocc/code/HEAD/tarball?path= Questions, bug reports or support requests are very welcome: https://sourceforge.net/p/nocc/_list/tickets Alternative source code repository: https://github.com/oheil/NOCC
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Proton Web Clients
Monorepo hosting the proton web clients
Proton Web Clients is a monorepo hosting the web applications for Proton’s suite of privacy-focused services, including the core Proton Mail webmail interface and related web apps like Proton Calendar, Proton Drive, Proton Account, Proton VPN, Proton Pass, and other connected tools. It consolidates all web client code, shared modules, dependencies, and development tooling into a single repository, enabling unified maintenance, consistency of design patterns, and efficient evolution of Proton’s online interfaces. These web clients run entirely in the browser, letting users securely interact with their email, calendars, files, and other services without needing native software installed, and benefiting from end-to-end encryption where applicable. The monorepo includes application logic, UI components, build scripts, and testing infrastructure for reliable deployments and streamlined continuous integration. -
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Mail Notifier
Mail Notifer for Windows
Mail Notifier is free, modern email notifier with the latest user interface trends for Windows 10/11. It supports multiple accounts and IMAP/POP3 protocols. Enjoy customizable notifications, message previews, and more, all in 34 languages! For more details, please refer to the readme.txt file (Files tab, description below). Note: Gmail support is currently unavailable due to verification requirements by Google. Note: Outlook.com support is currently unavailable due to moving to OAuth2 authentication from login/password at Outlook servers. -
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AfterLogic WebMail Lite PHP is a free AJAX webmail application. Users can receive, view, manage, compose, and send email through web interface (IMAP and SMTP supported). Source code included.
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Columba is an email client written in Java, featuring a user-friendly graphical interface with wizards and internalionalization support. Its a powerful mail management tool with features to enhance your productivity and communication.
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PHP app to access Gmail/Googlemail/Gmail-for-Your-Domain accounts on wireless devices. Convenient alternative access method to your email account on the move, gmail-mobile incorporates as many Gmail features as possible within limits of a mobile device.
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This is an open source Email client for Borland Delphi with source code. It uses Indy controls as well as PBears HTML Viewer Component and BSALA EmbeddedWB (updated versions for Delphi 2009 are here). It is IMAP, POP3, MAPI and SMTP compatible.
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GoldBug - Encrypted Communications
Chat Messenger. E-Mail-Client. Websearch. Filetransfer.
GoldBug is a decentralized & secure communication suite that offers an integrated e-mail client, an instant messenger & a file transfer. Also included is an URL-RSS-DB & a p2p web search. Current vers. w/ McEliece Algorithm. GoldBug has been 2013 - 2023 ten years just another Graphical User Interface of the Spot-On Encryption Suite. Main GUI features: Minimal & colorful Interface with Tabs in the East. Microsoft & Qt MinGW deprecated Win32 & for Compiling: ● https://sourceforge.net/p/goldbug/wiki/compiling As Spot-On implemented the minimal GB-concept & Nuvola Icons, GoldBug has now been fully integrated into Spot-On Win64: Just choose Tabs at East & Mini-View in Options - w/ Nuvola Icons of course! Voilá! & Many Thanks, Pro-Files can be found archived at ● current source: https://github.com/textbrowser/spot-on ● EN Manual: https://www.amazon.com/dp/3749435065 ● DE: https://compendio.github.io/goldbug-manual-de/ ● Study: https://www.amazon.com/asin/dp/3750408971 -
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MultiMail is an offline mail packet reader for Unix and other systems. It currently supports the Blue Wave, QWK, OMEN, OPX and SOUP formats. It has a full screen, color user interface, built with the curses library.
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JoeEmail - How Joe deals with Spam. JoeEMail is a lightly featured email client for windows that uses a Bayesian probability filter to detect and delete spam messages.
