Open Source Mac Email Clients
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Email Clients for Mac
View 41 business solutionsBrowse free open source Email Clients and projects for Mac 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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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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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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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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Meron
Fast, secure email client with chat and kanban views
Meron is a free, open-source email client designed to combine traditional email management with chat-style conversations and Kanban organization. It provides a unified inbox for managing multiple email accounts through IMAP and SMTP. Users can switch between conventional email, threaded chat, and Kanban board views. The software includes customizable tags, automated filtering rules, and rich-text message composition. It also supports RSS and Atom feeds for following online publications. Security features include encrypted local storage and credentials protected by the operating system's keyring. Optional Model Context Protocol integration allows AI clients to access permitted email functions. Available for Windows, macOS, Linux, Android, and iOS, Meron provides a flexible communication workspace. -
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mail
Built from the ground up for speed
Flectar Mail is an open-source email, calendar, and contact management application built with Rust for native performance and low memory consumption. It supports Windows, macOS, Linux, Android, and iOS, with mobile installation availability varying by platform. Users can connect Gmail, Outlook, Microsoft 365, and standards-based email services through IMAP, POP3, SMTP, and JMAP. Its interface organizes messages into conversation threads, tabs, and color-coded account profiles. CalDAV and CardDAV integration provides synchronized calendars and contacts. Offline storage keeps previously synchronized messages and information accessible without an internet connection. Security features include remote image blocking and native HTML rendering without executing email scripts. Additional capabilities include attachment searches, OpenPGP encryption, customizable themes, and local backups. -
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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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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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Aster Mail
Cross-platform encrypted email client for Aster
Aster Mail is an open-source, privacy-focused email service with cross-platform desktop and web clients. It protects messages, subject lines, and attachments between Aster users through local end-to-end encryption. Its cryptographic system combines ML-KEM-768 and P-256 ECDH with X3DH and Double Ratchet protocols for post-quantum protection. Messages sent to external recipients can use OpenPGP encryption when their public keys are available. Users retain control of their encryption keys and can export them to compatible applications. Optional key publishing enables encrypted communication with external contacts. Its zero-access architecture prevents the service from reading protected message contents. Accounts can be created without providing a phone number or recovery email. -
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Prospect Mail
Prospect is an Outlook mail desktop client powered by Electron
Prospect Mail brings Microsoft 365 Outlook email and calendar functionality to a dedicated desktop application. Built with Electron, it wraps Outlook's web interface for convenient access outside a regular browser. It supports Microsoft 365 accounts rather than personal Outlook.com accounts. Users can manage messages, appointments, and other available Outlook functions through the familiar interface. System notifications provide updates about new messages and calendar activity. The application supports spell checking through Microsoft Editor and PDF attachment previews. Its system tray controls allow minimized startup and background operation. Automatic session recovery helps restore authentication after expiration or system sleep. Prospect Mail runs on Windows, macOS, and Linux. -
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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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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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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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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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deltachat-desktop
Decentralized private messenger with chat-shared tools and games
deltachat-desktop is an open-source, decentralized messaging application that enables private communication through email-based messaging infrastructure. It provides a familiar instant messaging interface while using interoperable standards instead of relying on a centralized messaging platform. Conversations are protected with end-to-end encryption designed to safeguard messages against unauthorized access. Users can exchange messages, share media and files, and participate in group conversations. The application supports multiple profiles and devices, allowing users to manage communications across different environments. Its chatmail relay integration simplifies account creation and communication with other users. Interactive web applications can run directly inside conversations, enabling collaborative activities, games, and shared tools. Built with Electron, the desktop client is available for Windows, macOS, and Linux and includes customization options. -
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unimail-client
This is the first executable client program of Unimail
Unimail Client is a free, open-source command-line application for sending emails through the Unimail service. Built with Go, it uses the Unimail Go SDK to handle email delivery requests. Users can send plain-text messages or formatted HTML emails directly from a terminal. The application supports multiple recipients, carbon copies, blind carbon copies, and file attachments. API authentication can be configured through an environment variable or supplied with a command-line option. Routing parameters provide additional control over how messages are submitted. Built-in commands display version information, usage instructions, and available updates. Unimail Client can be integrated into scripts and automated workflows, with installation options for Windows and Linux. -
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G4J is a set of API that communicate to GMail. Use this API to login, retrive/search/browse message, download attachment and do others action on GMail account! An email application (Gmailer for java) is included to demonstrate the usage of the API.
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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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Hastymail is a fast, secure, rfc-compliant, cross-platform IMAP/SMTP client application written in PHP providing a clean web interface for sending and reading E-mail. This version of Hastymail is no longer being developed. We are now working on a new version, Hastymail 3, AKA, "Cypht". http://cypht.org
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Mailbird
All your email accounts in one place.
Mailbird is an intuitive email management application that brings all your email accounts together in one place, making it easier to manage your emails across both Windows and Mac devices. With a single license, Mailbird enables users to track emails, organize their inboxes, and integrate various third-party apps like Slack, Google Calendar, and Dropbox for enhanced productivity. Key features include AI-powered email drafting, customizable workspaces, and the ability to track email opens. Mailbird also offers the ability to block unwanted senders and unsubscribe from lists directly from the app. With over 4 million users worldwide, Mailbird has become a popular choice for professionals and businesses looking to enhance their email experience. -
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Email of Death is a browser based email client. 10-9-26: Fixed a couple of bugs. 11-8-26: Fixed a couple of bugs with the Android version.
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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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MH-E is the Emacs interface to the MH mail system. It offers all the functionality of MH, the visual orientation and simplicity of use of a GUI, and full integration with Emacs, including thorough configuration and online help. Since MH-E 8.6 was released in 2016, its development migrated to the Emacs repository. Thus, if you install an Emacs package, or check out and compile the Emacs source, then you will be running the latest version of MH-E. Consequently, we will retire this site once all of the tickets are resolved. Therefore, please help us out and submit new tickets with M-x report-emacs-bug. MH-E is now only supported in the version of GNU Emacs in which it appears. It is no longer supported in XEmacs. It is compatible with MH versions 6.8.4 and higher, all versions of nmh, and GNU mailutils 1.0 and higher.
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Is an ASP.NET webmail application written in C#. It uses a POP3 or IMAP servers as the mailstore and sends mail through a SMTP server. You can compose HTML messages, search your inbox, read complex mime messages and much more. .NET and Mono compatible.
