Citadel is an advanced messaging and collaboration system for groupware and BBS applications. Users can connect to Citadel using any telnet, WWW, or client software. Among the features supported are public and private message bases (rooms), electronic mail, real-time chat, paging, shared calendaring, address books, mailing lists, and more. Unlike other collaboration servers, Citadel provides its own data stores and is therefore extremely easy to install; you don't have to "bring your own" email and database because they're built in. The server is multithreaded and scalable. In addition, SMTP, IMAP, and POP3 servers are built-in for easy connection to Internet mail. Citadel is both robust and mature; it has been in production since 1987.
Claros inTouch is an AJAX Web mail, instant messenger, address book, and note taker application. The main features are drag and drop support, background attachment uploading, built-in Bayesian spam protection that can identify junk mail on the fly, folder support for the POP3 protocol, compatibility with any POP3/IMAP and SMTP server, operating system independence, support for sending HTML email, and full MIME compatibility. It also features a unique AJAX instant messenger that is capable of talking with a Jabber server.
CleanMail is a complete SMTP/POP3 email security solution that fights against spam and viruses. It works with any mail server like Microsoft Exchange 2003/2007/2010, Microsoft Small Business Server (SBS) 2003/2008, Lotus Notes/Domino, or IMail. CleanMail includes a comprehensive set of filters, including an attachment blocker, remote blacklist filter (DNSBL), and a complete build of SpamAssassin.
CleanPOP cleans your POP3 mailbox based on your local mbox, so local anti-spam tools can be applied to Web-mail and other non-local clients. After you've downloaded and processed mail from the POP server, CleanPOP logs in and purges email messages which match locally-added spam headers or are older than a configured expiration time. It aims to be safe by not deleting unfetched emails (unlike other email filters), and efficient by checking only new messages. It's also useful for fetchmail users, who have no option to "delete after X days".
Coherent Mail Gateway is intended to be a very easy to set up MTA using SMTP and POP3. Greylisting is used on the SMTP daemon to reduce spam. In addition, quite a lot of checks on the validity of information from the SMTP client (such as claimed server name and sender) are carried out, and anyone caught telling lies is disconnected. Grey-, black-, and white-listing are supported, as well as (optionally) ClamAV and Spamhaus. The target market is users with static IP addresses. Others can use the system, but its value will be limited to outgoing email.
Scalix Community Edition Raw (CE Raw) is functionally equivalent to Scalix's Community Edition software except that its components are individually available, making it easy to customize. It includes manual installation instructions via a community Wiki, with links to required third-party components. It is available for the Debian Linux distribution as well as Red Hat and SUSE Linux. The intent is to make it easy for Linux system admins, developers, and enthusiasts to to adapt an email and calendaring system for their needs and the needs of the community.
The Courier IMAP/POP3 maildir creation patch adds the ability to automatically create a user's home directory when he/she is successfully authenticated for the first time. It works by calling an admin-created script that takes care of creating the directory. It is quite useful in combination with authentication-modules based on network databases like MySQL or LDAP.
Cyrus2Dovecot is a full-featured command line tool for converting the email messages of one or more users from the Cyrus format to Dovecot Maildir++ folders. It allows you to perform a server transition which is fully transparent to both POP and IMAP users, as virtually all available metadata is preserved during the conversion. This includes message UIDs, INTERNALDATEs, IMAP folder subscriptions, the UIDVALIDITY and UIDNEXT values for each folder, as well as all IMAP flags (including the first 26 user-defined keywords).
The DBMAIL package replaces the normal UNIX mailing system. All email and user data is stored in a database. You can create an unlimited number of email accounts, which can be checked using the POP3 or IMAP protocol. Users can maintain their own set of email addresses. It is more scalable, more secure, and faster than traditional mail systems. DBMAIL has storage drivers for PostgreSQL and MySQL, and it has authentication drivers for PostgreSQL, MySQL, and LDAP.
DavMail is a POP/IMAP/SMTP/Caldav/Carddav/LDAP exchange gateway allowing users to use any email/calendar client (e.g. Thunderbird with Lightning or Apple iCal) with an Exchange server, even from the Internet or behind a firewall through Outlook Web Access. DavMail now includes an LDAP gateway to Exchange global address book and user personal contacts to allow recipient address completion in the mail compose window, and full calendar support with attendees free/busy display.