Balsa is a highly configurable and robust mail client for the GNOME desktop. It supports both POP3 and IMAP servers as well as the mbox, maildir and mh local mailbox formats. Balsa also supports SMTP and/or the use of a local MTA such as Sendmail.

OpenSMTPD is an implementation of server-side SMTP, with some additional standard extensions. It allows ordinary machines to exchange e-mails with other systems speaking the SMTP protocol, or to deliver them to local users.

In order to simplify the use of SMTP, OpenSMTPD implements a smaller set of functionality than those available in other SMTP daemons. The objective is to provide enough features to satisfy typical usage at the risk of unsuitability to esoteric or niche requirements.

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

Alot is a terminal-based mail user agent based on the Notmuch mail indexer. It is written in Python using the urwid toolkit and features a modular and command prompt driven interface to provide a full mail user agent (MUA) experience as an alternative to the Emacs mode shipped with Notmuch.

Mew (Messaging in the Emacs World) is a user interface for text messages, multimedia messages (MIME), news articles and security functionality including PGP, S/MIME, SSH, and SSL.

This Python module can be used to generate and parse RFC 5451/7001/7601 Authentication-Results email headers. It supports extensions such as:

• RFC 5617 DKIM/ADSP

• RFC 6008 DKIM signature identification (header.b)

• RFC 6212 VBR

• RFC 6577 SPF

• RFC 7281 Authentication-Results registration for S/MIME

• RFC 7293 The Require-Recipient-Valid-Since header field

• RFC 7489 DMARC

• ARC (draft-ietf-dmarc-arc-protocol-08)

Mlmmj is a simple and slim mailing list manager (MLM) inspired by ezmlm. It works with many different Mail Transport Agents (MTAs) and is simple for a system administrator to install, configure and integrate with other software. As it uses very few resources, and requires no daemons, it is ideal for installation on systems where resources are limited. Its features include:

1. Archive, Custom headers / footer,

2. Fully automated bounce handling (similar to ezmlm),

3. Complete requeueing functionality, Moderation functionality, Subject prefix,

4. Subscribers only posting, Regular expression access control,

5. Functionality to retrieve old posts, Web interface, Digests,

6. No-mail subscription, VERP support,

7. Delivery Status Notification (RFC1891) support,

8. Rich and customisable texts for automated operations.

nmail is an easily configurable terminal-based email client with a ncurses user interface similar to alpine and pine.

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.

The mblaze message system is a set of Unix utilities for processing and interacting with mail messages which are stored in maildir folders.

Its design is roughly inspired by MH, the RAND Message Handling System, but it is a complete implementation from scratch.

mblaze is a classic command line MUA and has no features for receiving or transferring messages; you can operate on messages in a local maildir spool, or fetch your messages using fdm(1), getmail(1), offlineimap(1), or similar utilities, and send it using dma(8), msmtp(1), sendmail(8), as provided by OpenSMTPD, Postfix, or similar.

mblaze operates directly on maildir folders and doesn't use its own caches or databases. There is no setup needed for many uses. All utilities have been written with performance in mind. Enumeration of all messages in a maildir is avoided unless necessary, and then optimized to limit syscalls. Parsing message metadata is optimized to limit I/O requests. Initial operations on a large maildir may feel slow, but as soon as they are in the file system cache, everything is blazingly fast. The utilities are written to be memory efficient (i.e. not wasteful), but whole messages are assumed to fit into RAM easily (one at a time).

This package takes your 48x48x1 portrait image and compresses it.

This package provides a CLI application to execute scripts on IMAP mailbox changes (new/deleted/updated messages) using IDLE and it is mostly compatible with the configuration of imapnotify made with Python.

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.

The sendgmail command provides a minimal sendmail-compatible front-end that connects to Gmail using OAuth2. It is specifically designed for use with git send-email. The command needs a Gmail API key to function.

Guix's version of sendgmail has been patched for compatibility with all known forks, including support for non-@gmail.com email addresses.

Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet. In style it is similar to Smail 3, but its facilities are more general. There is a great deal of flexibility in the way mail can be routed, and there are extensive facilities for checking incoming mail.

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.

neatmail is a noninteractive mail client. It generates a listing of the messages in a mailbox in mbox format and executes a list of ex-like commands on it.

MHonArc is a Perl mail-to-HTML converter. MHonArc provides HTML mail archiving with index, mail thread linking, etc; plus other capabilities including support for MIME and powerful user customization features.

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.

Mail::AuthenticationResults parses the message header field that indicates the message authentication status as per RFC7601. This module is not fully compliant with the RFC but it tries to implement most styles of Authentication-Results header seen in the wild.

GNU Mailman is software for managing email discussion and mailing lists. Both users and administrators generally perform their actions in a web interface, although email and command-line interfaces are also provided. The system features built-in archiving, automatic bounce processing, content filtering, digest delivery, and more.

Astroid is a lightweight and fast Mail User Agent that provides a graphical interface to searching, display and composing email, organized in thread and tags. Astroid uses the notmuch backend for searches through tons of email. Astroid searches, displays and compose emails — and relies on other programs for fetching, syncing and sending email.

Python module that implements DKIM (DomainKeys Identified Mail) email signing and verification (RFC6376). It also provides helper scripts for command line signing and verification. It supports DKIM signing/verifying of ed25519-sha256 signatures (RFC 8463). It also supports the RFC 8617 Authenticated Received Chain (ARC) protocol.

Email::MIME is an extension of the Email::Simple module, to handle MIME encoded messages. It takes a message as a string, splits it up into its constituent parts, and allows you access to various parts of the message. Headers are decoded from MIME encoding.