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.
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.
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
Sortmail is a program to process incoming email, classify it and
process it accordingly. Sortmail can handle incoming email as it
arrives or download from a POP server. Sortmail is easier to
configure than procmail and can replace fetchmail.
a lightweight ANSI C library for handling POP3 mailboxes
...libpop3 is written in pure ANSI C89 without any external dependencies, thus it can be compiled and used on anything, anywhere.
Since it is very light, it is designed to be used as a static library (but you could just as well incorporate its code right into your project).
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.
Sick of handling ifs and gotos in DOS batch files? Use this code generator to code in a higher level language, the sausage machine turns out the batch file. Mercurial repo at https://bitbucket.org/nickj/batchgen
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!
P3Scan is a fully transparent scanning proxy-server for email clients. It provides scanning of incoming/outgoing email messages for Virus''s, Worms, Trojans, Spam, and harmfull attachments. It can also parse messages for web-bugs.
vdpop3d has been designed to be secure, fast and reliable pop3 server. It's easy to configure, supports many authentication features, virtual users (per-domain auth, so the same user can exist in a lot of domains) and is thread based (scalability).
Fwsecvpop3d has been designed to be secure, fast and reliable pop3 server. It's easy to configure, supports many authentication features, virtual users (per-domain auth, so the same user can exist in a lot of domains) and is thread based (scalability).
pop3spam is a POP3 client which connects to a POP3 server and deletes
unsolicited mail in-place. It's possible to check for messages that exceed a
certain limit and to scan header lines for special patterns (regular
expressions).
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...
mpop3d is aiming to be a open-source modular POP3 server. Features incredibly powerful configuration management system, designed to be elastic so the administrator could easily achieve precisely what he wants.
Cyrus IMAPd is a popular IMAP server that surfaces a rich interface for extending its functionality. The Cyrus IMAPd Utilities project brings together maintenance utilities, graphical front-ends, and API handlers (such as notification daemons).
This project aims to be a personal data storage and administration system.
It will be an advanced system for information and electronic mail management. The server will be accessible to any IMAPv4 compatible mail client.
MailDB adds a database back-end to an IMAP server for features such as "virtual" mail folders (msgs appearing in multiple folders), "view" folders (dynamic results of searches), etc. The DB is inherently multi-user, allowing msg reference counting.
An open project for a number of activex controls for use in the Windows environment. The controls have been sold commerical before by Eurosource (http://www.eurosource.se) but are now free complete with source code.