Open Source Email Software

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.

K-9 Mail is an advanced, open-source email client for Android that's focused on making it easy to chew through large volumes of email. It's designed to be easy to use by both novice and power users, with plenty of useful features. It has IMAP push email support, support for multiple accounts, support for POP3 and Exchange 2003/2007 (with WebDAV), flagging, filing, signatures and more! K-9 Mail also offers a light and dark theme, keyboard shortcuts and emoji support. Like man's best friend, K-9 Mail is an email client you can depend on, and will surely be your best friend when it comes to handling your emails!

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.

SendMail is a simple program that can send e-mails via SMTP protocol. It is created using C# and is only available for Windows operating system. .NET Framework 4.8 is required to run the program.

SpamPal is a mail classification program that can help separate your spam from the mail you really want to read. SpamPal includes support for POP3, IMAP4 and SMTP accounts and can be extended by dozens of plugins and tools and is available in 6 languages

An SSL Postfix Management Interface in PHP/Ajax that handles all postfix parameters including Virtual Domains in LDAP.It handles all securities features by implementing all addons like Spamassassin,Clamav,Milter-greylist,amavis within technical skills

GreenMail is an intuitive and easy-to-use test suite of email servers for testing purposes. Supports SMTP, POP3, IMAP with SSL socket support, and configurable user accounts and credentials. All in 100% Java. WE'VE MOVED TO GIT HUB: https://github.com/greenmail-mail-test/greenmail

Hedwig is an open source IMAP, SMTP, POP3 server written in Java, designed with ease of installation and configuration in mind. Hedwig enables storage of mail message headers in a relational database(MySQL or Oracle) and mail messages in a file system. Visit http://hwmail.sourceforge.net/ for more information.

SpamAssassin for Win32 is a free and powerful anti-spam filter for Windows. Includes a resident daemon for mail servers and a user-friendly personal spam filter that works with any POP3 account and any email client.

icarusWebMail is an open source WebMail, with POP3 and IMAP mailbox support, also supports APOP POP3/SSL POP3/TLS IMAP/SSL contacts lists from LDAP, anti-spam integration, Internationalization (by now es, en, fr), Filters, Drafts, Sent-Folder, Signature.

Konfidi is a trust framework that uses topical trust values from a social network of authenticated people. When you receive an email from someone you do not know, but he/she is in the network, Konfidi will compute an inferred trust value for you.

Free and light e-mail alert client. Multi-profile and multi-account support. Support for IMAP and IMAPS. Built-in settings for the most popular e-mail services (1&1, AOL, GMail, Hotmail, MobileMe, Yahoo! Mail, etc).

A.I. security app. Development ceased.

Simple Ajax Wiki that stores wiki pages into FileSystem or Subversion. It uses wikimodel syntaxe, JQuery for HTML DOM manipulation, DWR for Ajax and Spring for J2EE

This project is a C++ library which allows incorporating DKIM into an existing MTA or other application. It provides full support for signing, verifying, and SSP. It is compliant with RFC 4871.

AmavisAdmin is a tool to maintain SPAMs, Viruses and blocked mails written to an SQL database by Amavisd-new. Mails can be removed automatically or manually, or they can be released to be send to the recipients.

Arcjet helps developers protect their apps in just a few lines of code. Implement rate limiting, bot protection, email verification, and defense against common attacks. Native security for Bun, Next.js, Node.js, SvelteKit, Vercel, Netlify, Fly.io, and other modern platforms. Customizable protection for signup forms, login pages, API routes, and your whole app. Test security rules locally. Protection that works in every environment. No agent is required.

AtMail is an open source webmail client written in PHP. We aim to provide a elegant Ajax webmail client for existing IMAP mailservers, with less bloat and a focus on an intuitive, simple user interface.

Mail Web Frontend based on Tapestry, Spring and Hibernate. Configure several accounts with one account

MobileCLI provides .NET ECMA-compatible runtime engine and library for develop mobile application on BREW, Symbian.

CURE provides a web-based environment for distributed collaboration. It was designed for lerning groups but is now also used to support busines collaboration. It combines wiki ideas with mailing lists, shared folders, chats, and room metaphors.

Clarke is a Perl script for automatically replying to email. It has a featureful command line, and can be run from a .forward or .qmail file or interactively. It is used by The Apache Software Foundation.

Community-based interoperability Utility for SMEs. Commius main objective is to support the SMEs with a zero, or very low-cost, entry into interoperability, based on non-proprietary protocols. Commius is an EU-FP7 funded project.

CaMath is a common model of "Cost Accounting",written by C++ and C#.

DKIM for JavaMail is a small JAR that can be easily implemented in existing Java projects using JavaMail for sending DKIM signed emails.