Open Source Linux Mail Transfer Agents

E-MailRelay is a simple SMTP proxy and relay MTA, written in C++, for Linux and Windows. As a proxy all messages can be passed through a user-defined program, such as a spam-filter, which can drop, readdress, or edit messages as they pass through.

The Courier mail transfer agent (MTA) is an integrated mail/groupware server based on open commodity protocols such as ESMTP, IMAP, POP3, LDAP, SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, Webmail, calendaring, and mailing list services.

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.

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

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.

YPOPs! is an application which emulates a POP3/SMTP mail server and provides free POP3 and SMTP access to Yahoo! Mail. It does not depend on Yahoo's POP3/SMTP mail server. You can use a mail client of your choice!

The goal of this project is to develop a very simple SMTP server that responds to SMTP requests and makes received messages available for query at a later time. All useful features for a SMTP server that can be used in an automated testing suite.

Pure Perl implementation of the Milter protocol used by Sendmail, including drop-in replacement for the Sendmail::Milter interface.

An advanced qmail distribution based on qmail-sql which has SMTP, SMTPS, POP3, POP3S, IMAP, IMAPS services, a content scanner, spoofing protections, SMTP AUTH support, SMTP-after-POP/IMAP, PHP5 API, SPF support and much more...

ESMTP MTA is a user configurable relay-only MTA with a sendmail-compatible syntax, based on libESMTP and supporting the AUTH (including the CRAM-MD5 and NTLM SASL mechanisms) and the StartTLS SMTP extensions.

Rumble is a mail server suite for SMTP (ESMTPSA), HTTP, POP3 and IMAP4v1 with an extensive C/C++ and Lua API for scripting. It comes with support for SSL/TLS, SQLite and MySQL and has a web-based administration and webmail feature. Additional included modules feature greylisting, DNS blacklisting, SpamAssassin support and dynamic performance scaling as well as a multithreaded structure that allows for clustering of multiple servers for one or all domains, and with the ease of the Lua API, you can create your own new server mailing lists, CRM software, e-marketing and other extensions within minutes.

ZMail allows you to send email from anyone, to anyone. You can use ZMail to send fake or anonymous emails. Have fun!

MSWeb is a client for Microsoft's Outlook Web Access (OWA). It is intended to deliver mail from a MS exchange server to a UNIX computer. For those who are opposed to 50 MB mailreaders.

Tools for a mail delivery service, including LMTP and POP3 servers and also getpwnam() emulation. Mail is stored in Maildir++ format (qmail plus courier extensions as soft quota and subfolders). User defined filter and virtual domains are supported.

Python API for Sendmail Milters. Related modules provide features such as content filtering, SPF, and reputation tracking. Changes are posted first to https://github.com/sdgathman/pymilter and related repos.

jwSMTP, Send email programmatically (C++ code/lib). Linux, BSD, Windows etc. Attachments, Multiple recipients, Cc/Bcc recipients supported. MX lookup or send to an SMTP server direct. LOGIN and PLAIN authentication now supported. Html or plain text forma

MailArchiva is a powerful, full featured email archiving (email archiver) and compliance solution for mail systems such as Microsoft Exchange. It stores all incoming, outgoing and internal emails for long term storage. A web based user interface is avail

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

TMDA is an open source anti-spam system and local mail delivery agent written in 100% pure Python. TMDA combines whitelists, blacklists, a challenge/response system, and special-purpose e-mail addresses called "tagged addresses" to thwart spam.

The Exim Ldap Mail Administrator is a webfrontend for your mailserver environment running EXIM with LDAP. It supports multiple virtual maildomains including users and aliases. Filter and vacation settings will be available soon.

JEM is an SMTP server with pluggable components that let you process email in any way you like. It can also extend beyond emails into generalised message processing (like JMS) and can even generate its own messages based on a Cron-like facility.

Mailster is a project aimed at testing software mail capabilities. It provides a mail server container to test emails sent by your apps without rewriting your application code.

The OpenPEC project is a collaborative effort to develop an Open Source Certified E-Mail System (in italian: Posta Elettronica Certificata or PEC) as requided by the Italian law. See the DigitPA (CNIPA) site for details (http://www.cnipa.gov.it)

Rigel is an RSS to IMAP gateway written in perl based upon rss2imap. Rigel is intended to allow a user to directly place RSS articles in an IMAP server of thier choice.

Provide an Open Source Java Email Server that supports POP3/SMTP.