Open Source Email Software - Page 2
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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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Isync
mailbox synchronizer
A command line utility for synchronizing remote IMAP mailboxes and local maildir-style mailboxes. This is useful for working in disconnected (off-line) mode, such as on a laptop, but also for mirroring mailboxes between servers. -
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mailsend
A program to send mail via SMTP from command line
mailsend is a simple command line program to send mail via SMTP protocol. It can send a piece of alert mail from a program in a networked Windows machine. It's feature-filled, cross-platform, free and open source, and does not use any config file. -
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Thunderbird for Android
Open Source Email App for Android (fka K-9 Mail)
Thunderbird Android is the mobile counterpart of the popular Thunderbird email client, reimagined for Android phones and tablets so users can access, send, and organize email from multiple accounts with advanced features found in desktop clients. It embraces modern mobile UI design while supporting robust email protocols (IMAP/POP3) and standards like OAuth for secure logins to services such as Gmail, Outlook, or custom mail providers. The app is built to handle complex mailbox structures, threaded discussions, rich text and HTML content, attachments, and account synchronizations reliably even on cellular connections. With features like unified inboxes, background fetch, push notifications, and configurable swipe actions, Thunderbird Android aims to bring the power and flexibility of the desktop experience to your pocket. It also integrates search, filtering, and tagging capabilities that help users stay organized when managing large volumes of mail. -
MongoDB Atlas runs apps anywhereMongoDB Atlas gives you the freedom to build and run modern applications anywhere—across AWS, Azure, and Google Cloud. With global availability in over 115 regions, Atlas lets you deploy close to your users, meet compliance needs, and scale with confidence across any geography.
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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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Highly scalable/configurable Messaging Platform allowing users in a domain to be distributed on multiple hosts, has multiple queues. Provides virtual domains/users in MySQL. Modern MSP class qmail replacement with ESMTP, POP3/IMAP, QMTP, QMQP support
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LogicMail is a standalone E-Mail client designed to run on RIM BlackBerry handheld devices, providing full support for IMAP, POP, and SMTP over the device's Internet connection. Its exists to provide an alternative to the service-oriented "push" E
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Fetchmail - the mail-retrieval daemon
Client daemon to move mail from POP and IMAP to your local computer
Fetchmail is a mail retrieval daemon that can download messages from POP3, IMAP, ODMR and ETRN-based stores, with SSL/TLS security including certificate verification, and pass downloaded mail to a local SMTP or LMTP server, or a message delivery agent such as maildrop. -
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Google Apps Manager
Command line management for Google G Suite
Google Apps Manager or GAM is a free and open source command line tool for Google G Suite Administrators that allows them to manage many aspects of their Google Apps Account quickly and easily. With GAM you can create and manage users, groups and domains; manage email, security and calendar settings; manage admins and organizations and many more. To use GAM Google Apps Business, Education, Partner or Government Edition is required. -
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MOSINT
An automated e-mail OSINT tool
MOSINT is the fastest OSINT Tool for emails. It helps you gather information about the target email. Email validation, check social accounts, check data breaches and password leaks, finding related emails and domains, scan Pastebin Dumps. Google Search and DNS Lookup. -
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PostfixAdmin is a Web Based Management tool created for Postfix. It is a PHP based application that handles Postfix Style Virtual Domains and Users that are stored in MySQL, PostgreSQL or SQLite
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Proton Mail for Android
Proton Mail Android app
Proton Mail for Android is the official mobile application that lets users access their Proton Mail encrypted email accounts securely on Android devices, providing the full suite of messaging features while preserving end-to-end encryption and user privacy. Designed for modern Android phones and tablets, the app lets users send, receive, organize, and search encrypted emails, create new Proton accounts, manage multiple accounts, and apply labels or folders to keep messages tidy — all within a responsive, touch-optimized interface. It supports composing messages, viewing attachments, handling contacts, and configuring account and mail settings from within the app, giving users portable access to their secure inbox wherever they go. Because ProtonMail’s service never sees unencrypted content, the Android client performs necessary encryption and decryption on the device, aligning with Proton’s privacy-first philosophy and open-source security model. -
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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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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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Send SMTP email silently from command line (CLI), or a batch file using Exchange, Gmail, Hotmail, or Yahoo! Plus. Supports XML settings files, variables, or all settings explicitly from the command line. Now supporting Exit Codes for batch file use (will return "0" for successful delivery, or "1" for error delivering) - handle your batch file accordingly.
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base64 RFC1113 Vanilla ANSI-C Code for a portable stand-alone file encode/decode utility. In 2001, I asked people to 'Help me break it!' Since then, 10+years later, the code remains unbroken and is in wide production use world-wide. It has been ported to all major architectures and been used as a template for ports to different computer and human languages. This is very mature and stable code. Although this comes from a project that was constrained by export controls and is used in secure systems, it is not security code per-se. I have therefore altered the 'Export Controls' category.
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Bubbles
Bubbles the simple, easy to use HTTP web server, browser controlled
Bubbles the simple, easy to use HTTP web server that is browser controlled, and capable of serving static files over the internet, either streamed from disk, or direct from RAM without lag. A GUI administration panel is accessed through your web browser (e.g. "http://localhost:1080/admin/" + default password of "admin"), which controls all her settings and vital functions, all in real time. Apart from serving files, she is capable of tracking site visits (site counters), receiving emails, accepting contact form submissions with support for Spam Guard, and recording site activity as date stamped traffic logs. She also includes a built-in log analyser for making sense of her traffic logs. These and other features make her more than capable of running multiple websites with little to no headache. Her design is light and stable, and an extensive block-based memory management system ensures all her key operations use memory in a sustained and reliable manner. -
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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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MailSlurper
Local, web-based mail server application. Slurp mails into oblivion!
MailSlurper is a small SMTP mail server that slurps mail into oblivion! MailSlurper is perfect for individual developers or small teams writing mail-enabled applications that wish to test email functionality without the risk or hassle of installing and configuring a full-blown email server. It's simple to use! Simply set up MailSlurper, configure your code and/or application server to send mail through the address where MailSlurper is running, and start sending emails! MailSlurper will capture those emails into a database for you to view at your leisure. The following are general instructions for compiling MailSlurper. Your details may vary a bit here and there. The below example is based on a Unix-style system, such as Ubuntu or OSX. Furthermore, for instructional purposes, it is assumed that your GOPATH is set to ~/code/go, and that you have a folder in your source directory called github.com. Your setup may vary. -
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Mailtrain
Self-hosted newsletter app
Mailtrain is an open source, self-hosted newsletter application that allows you to easily manage your subscriber lists, even with a very large number of subscribers. Whether you have a thousand or a million subscribers, Mailtrain can keep you on top of things by letting you add subscribers manually, through the API, or import from a CSV file. Built on Node.js (v7+) and MySQL (v5.5+ or MariaDB), Mailtrain comes with an excellent set of features, including a wide range of custom fields, list segmentation, template editors, automation and more. It also allows you to check click statistics of every link included in your campaign. -
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Proton Mail for iOS
Secure email that protects your privacy
Proton Mail for iOS is the official iPhone and iPad client that brings Proton’s secure, end-to-end encrypted email service to Apple’s mobile ecosystem, combining strong privacy protections with native performance and gestures. The app allows users to sign in to one or multiple Proton Mail accounts, read and compose encrypted messages, schedule emails, protect emails with passwords, set expiration timers, and organize mail with labels and folders inside a smooth, intuitive iOS interface. It makes use of Apple’s networking APIs and encryption frameworks to deliver seamless management of encrypted communications while respecting platform conventions like touch navigation, Apple notifications, and background refresh. All sensitive operations — including key handling and encryption — occur locally on the user’s device, ensuring that plaintext messages and secret keys are never exposed to Proton’s servers or third parties. -
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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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reg-factory
Google Mail registration
reg-factory is an automation-oriented account registration pipeline aimed at research, testing, and controlled platform workflow experiments. It combines browser automation, environment-based configuration, and a local web control panel to run multi-step registration scripts. The project includes modules for email registration, platform sign-up flows, token handling, cookie export, and account workflow management. It uses local scripts and external tool integrations to coordinate browser profiles, network settings, Android-based Gmail workflows, and runtime logs. The included panel helps users launch scripts, fill parameters, monitor tool status, and review process output from one place. Because the project touches sensitive account-creation workflows, it should only be used in authorized, compliant, and non-abusive testing environments. -
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(This site is DEPRECATED. Please visit https://github.com/verdammelt/tnef) TNEF provides a way to unpack those pesky Microsoft MS-TNEF MIME attachments. It operates like tar in order to upack any files which may have been put into the MS-TNEF attachment instead of being attached seperately.
