getmail is intended as a simple, secure, and reliable replacement for fetchmail. It retrieves email (either all messages, or only unread messages) from one or more POP3, SPDS, or IMAP4 servers (with or without SSL) for one or more email accounts, and reliably delivers into qmail-style Maildirs, mboxrd files, or through external MDAs (command deliveries) specified on a per-account basis. getmail also has excellent support for domain (multidrop) mailboxes, including delivering messages to different users or destinations based on the envelope recipient address.
isync is a commandline application which synchronizes a local maildir-style mailbox with a remote IMAP4 mailbox, suitable for use in IMAP-disconnected mode. Multiple copies of the remote IMAP4 mailbox can be maintained, and all flags are synchronized. TLS/SSL is supported via imaps: or STARTTLS.
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.
OpenGroupware.org is a set of applications for contact, appointment, project, and content management. It is comparable to Exchange and SharePoint. It is accessible using Web interfaces or using local clients via WebDAV, GroupDAV, and CalDAV. Custom applications can be developed using the XML-RPC API. OpenGroupware.org runs on almost every GNU/Linux system.
TWIG is a Web-based groupware suite written in PHP, compatible with both PHP3 and PHP4. Its features include IMAP and POP3 email, Usenet newsgroups, contact management, scheduling, shared notes and bookmarks, a todo list, and meeting announcements. Any piece of information can be shared with others via group oriented access controls. By using only plain HTML, it is a simple, cross-platform, fast, and browser-independent way to access or share almost any kind of information, without the complexity or costs of other intranet/groupware packages. It is fully internationalized, with 24 translations.
XCmail is a MIME and multi POP3 capable mailtool for X11 using the Xclasses X11 layout library. Its main purpose is to read and write mail, allowing any kind of data to be attached. It can handle MIME types, has helpers to show different types, and can encode and decode binary data into ASCII to allow it to be transported as mail over the Internet. It has many built-in functions such as 2 vCards, unlimited POP3 servers, SMTP, SMTP after POP3, SMTP-AUTH (RFC2554), addressbook, encoders, filters, a special spam filter, spell checker, xface, and a new "virtual folder" concept. It also uses external programs to enhance its feature set. XCmail can be extended through a plugin interface.
XFMail is an X11 application for receiving electronic mail. It implements most of its email functionality internally so that it does not depend on a lot of extra packages. It supports POP3, MBOX, IMAP4, sendmail, and SMTP. It has built-in support for interfacing with PGP, GPG, ispell/aspell, faces, LDAP, and esound. It runs on most Unix variants.
ADJE WebMail is a set of Perl CGI scripts which provide a Web interface to existing email accounts on any POP3-compliant email server. The software provides a complete interface, including encoding/decoding attachments, email and URL markup in received emails, and an address book for each user.
kmMail is a PHP-based mail program, based on the mail functionality of Keftamail and is being developed by current Kefta employees. It is meant to be a framework for putting a web-based mail program on your site, but is still robust enough to drop into your current site with little to no modification. The goals of kmMail are MIME compliance, speed, low overhead, and an enjoyable user interface.