The hyperkitty Django app provides a web user interface to access GNU Mailman3 archives, and manage it. This interface uses django, and requires some configuration.

Bogofilter is a mail filter that classifies mail as spam or ham (non-spam) by a statistical analysis of the message's header and content (body). The program is able to learn from the user's classifications and corrections. It is based on a Bayesian filter.

CRM114 is a system to examine incoming e-mail, system log streams, data files or other data streams, and to sort, filter, or alter the incoming files or data streams according to the user's wildest desires. Criteria for categorization of data can be via a host of methods, including regexes, approximate regexes, a Hidden Markov Model, Orthogonal Sparse Bigrams, WINNOW, Correlation, KNN/Hyperspace, or Bit Entropy (or by other means--it's all programmable).

Procmail is a mail delivery agent (MDA) featuring support for a variety of mailbox formats such as mbox, mh and maildir. Incoming mail can be sorted into separate files/directories and arbitrary commands can be executed on mail arrival. Procmail is considered stable, but is no longer maintained.

Email::Address implements a regex-based RFC 2822 parser that locates email addresses in strings and returns a list of Email::Address objects found. It is recommended to use Email::Address::XS instead.

OfflineImap synchronizes emails between two repositories, so that you can read the same mailbox from multiple computers. It supports IMAP as REMOTE repository and Maildir/IMAP as LOCAL repository.

Khard is an address book for the console. It creates, reads, modifies and removes CardDAV address book entries at your local machine. For synchronizing with a remote address book, vdirsyncer is recommended. Khard can also be used from within the email client mutt.

Urlscan is a small program that is designed to integrate with the Mutt mail reader to allow you to easily launch a Web browser for URLs contained in email messages. It parses an email message or file and scans it for URLs and email addresses. It then displays the URLs and their context within the message, and allows you to choose one or more URLs to send to your Web browser. Alternatively, it send a list of all URLs to standard output. It is a replacement for the urlview program.

The mailmanclient library provides official Python bindings for the GNU Mailman 3 REST API.

Technology for Resting Email Encrypted Storage (TREES) is a NaCL-based Dovecot encryption plugin. This plugin adds individually encrypted mail storage to the Dovecot IMAP server. It is inspired by Posteo's scrambler which uses OpenSSL and RSA key pairs. TREES works in a similar way, but uses the Sodium crypto library (based on NaCL).

How it works:

1. On IMAP log in, the user's cleartext password is passed to the plugin.

2. The plugin creates an argon2 digest from the password.

3. This password digest is used as a symmetric secret to decrypt a libsodium secretbox.

4. Inside the secretbox is stored a Curve25519 private key.

5. The Curve25519 private key is used to decrypt each individual message, using libsodium sealed boxes.

6. New mail is encrypted as it arrives using the Curve25519 public key.

fdm fetches and delivers mail in various ways.

Mail may be fetched from IMAP or POP3 servers, from local maildirs, or read from standard input. It is then filtered based on regular expressions, its size or age, or the output of a (shell) command. It can be rewritten by an external process, dropped, left on the server or delivered into maildirs, mboxes, to a file or pipe, or any combination.

fdm is primarily designed for use by a single user, but can use privilege separation to safely deliver mail in multi-user setups.

Mu is a tool for dealing with e-mail messages stored in the Maildir format. Mu's purpose in life is to help you to quickly find the messages you need; in addition, it allows you to view messages, extract attachments, create new maildirs, and so on.

Cyrus IMAP is an email, contacts and calendar server. It provides support for a variety of protocols including JMAP, IMAP/IMAP-S, and POP3/POP3-S as well as CalDAV and CardDAV.

pan is a Usenet newsreader that's good at both text and binaries. It supports offline reading, scoring and killfiles, yEnc, NZB, PGP handling, multiple servers, and secure connections.

Email::Sender replaces the old and sometimes problematic Email::Send library.

Postorius is a Django app which provides a web user interface to access GNU Mailman.

Mail::SPF is the Sender Policy Framework implemented in Perl.

TNEF is a tar-like program that unpacks MIME attachments of type application/ms-tnef.

This package provides an Emacs-based interface to the Notmuch mail system.

Muchsync brings Notmuch to all of your computers by synchronizing your mail messages and Notmuch tags across machines. The protocol is heavily pipelined to work efficiently over high-latency networks such as mobile broadband. Muchsync supports arbitrary pairwise synchronization among replicas. A version-vector-based algorithm allows it to exchange only the minimum information necessary to bring replicas up to date regardless of which pairs have previously synchronized.

Birdtray is a free system tray notification for new mail for Thunderbird/Icedove. Its features include an unread mail counter, snooze-able new mail notifications, configurable fonts for different accounts, a ``quick compose'' function with pre-configured templates, and a direct connection to the Thunderbird database, making it completely independent from the extension API.

Swaks is a flexible, scriptable, transaction-oriented SMTP test tool. It handles SMTP features and extensions such as TLS, authentication, and pipelining; multiple versions of the SMTP protocol including SMTP, ESMTP, and LMTP; and multiple transport methods including unix-domain sockets, internet-domain sockets, and pipes to spawned processes. Options can be specified in environment variables, configuration files, and the command line allowing maximum configurability and ease of use for operators and scripters.

afew is an initial tagging script for notmuch mail. It provides automatic tagging each time new mail is registered with notmuch. It can add tags based on email headers or Maildir folders and can handle spam and killed threads.

A schema-driven command line tool for administering Stalwart Mail and Collaboration Server over its JMAP API.