Open Source C Post-Office Software

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.

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.

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.

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

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.

Heirloom mailx (formerly known as "nail") is intended provide the functionality of the POSIX mailx command with additional support for MIME messages, IMAP (including caching), POP3, SMTP, S/MIME, message threading/sorting, scoring, and filtering.

Watch mailstores for changes and initiate mailbox syncs

FreePOPs is a webmail to pop3 conversion daemon. It is extensible to support other webmail using the scripting language LUA. See the homepage for supported webmails.

smm is a anti-spam, mail-shaper, delete-on-server software thought for users who have a slow dialup connection and are sick and tired of downloading 1MB a day of spam and Win32-worm-attached messages.

Pulsar POP3 server (daemon) is easy to use with intuitive configuration file. It supports virtual (non-system) users and virtual hosts (IP based and user supplied). Can run from xinetd, inetd or standalone.

Simple and flexible checkpassword interface packages. POP, APOP, Multiple maildirs per user, Multiple password per maildir and Multiple virtual domains are supported.

ClamMail is POP3 email proxy for Windows with integrated ClamAV antivirus engine. ClamMail is an Windows antivirus that protects your PC from viruses transferred via mail. Works with Outlook,Thunderbird,Eudora and many others using popular POP3 protocol

K-POP, A project to create a new, innovative, and flexible POP3 Server.

libpop3 is a very light POP3 library for C. It allows to list, fetch and remove messages from a POP3 mailbox. This library is using the RFC1939 as reference, and uses most basic POP3 commands to provide maximum compatibility across different servers. 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).

Mailcheck is a simple, command line, configurable tool that allows multiple mailboxes to be checked for the existence of new mail messages. It supports both mbox and maildir-style mailboxes. It also supports remote POP3 and IMAP mailboxes.

APOP + LDAP authentication patch for QMail (auth_pop) 1. POP & APOP authentication 2. Passwords in LDAP are stored encrypted

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.

Checkpop is a POP3 command line interface for UNIX based operating systems.

Web-interface management for virtual domains, email-addresses and aliases for the courier mail server. Depends on MySQL and PhP

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).

FLOPP Project is an open POP Proxy. It supports many features, including commands filtering and logging, multiple cascaded proxies, in/out access lists, statistics, etc..

GeoSync aims to add support for DPOP3 (extensions to POP3 to add IMAP-like features) to GNU-pop3d

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...

IDMS DBMA is an effort to develop a highly scalable (c10k complient) plugin based mail agent aimed at fighting spam & viruses. Hopefully replacing hard-to-maintain, complex, resource hungry configurations used by small to large users today.