BrowserExpress is a Web-based e-mail client. BrowserExpress provides a Web browser interface to any mail server, giving all your users Web-based e-mail from any Web browser. The BrowserExpress interface is fully customizable to support your branding, banner advertisements, and language choice. BrowserExpress implements POP3, SMTP, LDAP, and MIME standards.
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.
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.
MailMan is one of the most stable, mature, and robust Web-based email systems available. The overall goal of the system is to provide the simplest possible way to add a Web-based email system to any Web site, so ease of installation and maintenance was the first goal in MailMan's design. It has no dependencies and no known incompatibilities with any Web server or mail server. It supports sending and receiving attachments, a single-frame or multi-frame interface, HTML-formatted messages, user options, address books, mail folders, and more.
Ledmail is a small mail checking utility that utilises the keyboard LEDs (caps, num, and scroll lock) to indicate when new mail has arrived. The LEDs are made to flash in an answerphone-like manner to indicate the number of new messages that are present in given mail servers. Each LED can be given a separate list of mail servers to poll, and the total number of new messages on those servers will determine how many times the LED will flash. Errors in checking mail servers cause the LEDs to flash in an inverted state, or to stay on. Ledmail can check both POP3 and IMAP4 mail servers.
Heirloom mailx (formerly known as "nail") is derived from Berkeley Mail and provides the functionality of the System V and POSIX mailx commands. Additional features include support for MIME, IMAP (including caching and disconnected use), POP3, SMTP, S/MIME, international character sets, maildir folders, message threading, powerful search methods, scoring, and a Bayesian junk mail filter. Mailx can be used as a mail batch language in nearly the same way as it is used interactively. It can thus act as a mailbox filter, can fetch mail from remote accounts, and can send files as attachments.