akpop3d is a POP3 daemon aimed to be small and secure. Despite its small size, it offers a lot of features. It is completely RFC 1939 compliant.
ccpop is a POP3 mail notify daemon with support for multiple mailboxes. The daemon will periodically check a remote POP3 mailbox for changes and notify the user by playing an audio file if new mail has arrived. The script is small, full configurable, efficient and written in Python.
Checklocalpwd is an alternative "checkpassword" program for the Qmail POP server.
Dovecot is an open source IMAP and POP3 server for Linux/UNIX-like systems, written with security primarily in mind. Although it's written in C, it uses several coding techniques to avoid most of the common pitfalls. Read more
FreePOPs is a POP3 server that is scriptable in LUA. Plugins are currently implemented for using FreePOPs as an RSS aggregator, a POP3 forwarding server, and a POP3 interface to webmail services.
hotwayd/hotsmtpd are POP3/SMTP-HTTPMail gateway daemons. The HTTPMail protocol is used by the mail servers Hotmail, Lycos, Spray and MSN. The hotway suite you can receive and send mail via these services using any POP3/SMTP compliant mail reader.
(commercial) a secure Internet and intranet email server for mid-sized businesses. It incorporates anti-virus control, SSL encryption of POP3, IMAP4, SMTP, WebMail (HTTP), and WAP protocols, attachment/content filtering, and MAPS/user-defined anti-spam database. It offers support for multiple domains, automated replies, SMS notifications, shared and public folders, email folder backup, and encrypted remote administration
An almost rfc1939 compliant POP3 server. The main goal of this program is the speed, especially if you have many mails in your maildir (>4000) and you want to store your mails on the server.
maildirpop3d offers multiple POP mailboxes (with distinct passwords) controlled by a single shell account. It is a checkpassword replacement, and sits between qmail-popup and qmail-pop3d.
Mailnag is a daemon program that checks POP3 and IMAP servers for new mail. On mail arrival it performs various actions provided by plugins.
NullPop is a POP3 server that allows logins, but never returns any email. This is useful for certain setups where the user needs an 'account' setup in their mail client, but no real mail will ever be received.
a GPL'd POP3 server designed for high-performance (read: large user) enviroments. In particular, it optimizes for the best case POP session, where a user has no new mail and is simply receiving the same UIDL/STAT information as before
a patch that enables cucipop to use the PAM authentication mechanism
Perdition allows users to connect to a content-free pop server that will redirect them to their real pop server. This enables pop for a domain to be split across multiple real pop servers on a per user basis.
Perl Pop3 is a POP3 server fully implemented in Perl. The advantages over other POP3 servers are that it is not a memory hog, and can be used to connect to databases for authentication.
poop POP3 Server
a small and simple POP3 server designed to work with the V Mail Server (but not exclusively)
a daemon for use with Postfix which allows users to authenticate using POP3 so that they can send email by SMTP
POP-Before-SMTP-Auth is a POP before SMTP daemon for Dovecot and Postfix that works by scanning mail server log files.
a flexible, RFC 1939 compliant Post Office Protocol 3 daemon. It implements everything mentioned in the RFC
a tiny POP3 daemon, designed with security as the primary goal
a Perl-based daemon that uses POP to authorize connecting hosts for SMTP relaying, or forwarding, of mail through the server
poplimitd produces a daemon that provides a method to track generic POP3 or IMAP logins on UNIX type systems
Poprox is a POP3 and SMTP transparent filtering proxy. It does virus scanning using libclamav and is comparable to p3scan in philosophy.
POPular is a suite of programs for setting up large scale POP3 server systems. It consists of a POP3 proxy, a storage server and lots of utility programs.
Relay4exim is a small daemon for Linux that permits POP-before-relay (also known as POP-before-auth) for Courier-IMAP and Exim. Exim is a popular SMTP email server (MTA), and Courier-IMAP is a popular POP3 and IMAP4 server (MDA). When a user successfully logs in to Courier-IMAP to retrieve their email messages, Relay4exim permits their IP address to promiscuously relay messages through Exim.
smunge is a standalone POP3 funneling proxy server, designed to allow clients to attach to multiple pop servers as if they were one.
Snowbox is a POP3 server written in Perl. The goal of Snowbox is to have a very secure POP3 server that doesn't suffer from the usual security problems many implementations in C do.
Solid POP3 Server
Solid POP3 Server is an implementation of a Post Office Protocol version 3 server that has flexibility as its main goal. It has has support for few features such as APOP authentication scheme, virtual hosting, maildir and mailbox handling, bulletins &expiration of messages.
yet-another-pop3-server. The intention has been to write a server which is fast, extensible, and secure. `Extensible' is used specifically in the context of new authentication mechanisms
a POP2/POP3/IMAP Server with linuxconf virtual domain support based on WU-IMAP
a POP3 server. It is free to download and use. It supports alternative password files and mail spool directories; it can be used for setting up virtual email accounts -- mailboxes without real Unix owners for each
a complete virtual domains email setup, including sample Exim configuration sections, a patch to gnu-pop3d, and a set of scripts for administrating domains
VPOP3 is an innovative RFC-compliant POP3 server with a bunch of exclusive features which guarantees you a major flexibility.
zpop3d is a RFC 1939-compliant POP3 server. It features virtual domains support, POP before SMTP, and secure mailbox updates.