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

Mail::DKIM is a Perl module that implements the DKIM standard, and the older Yahoo! DomainKeys standard, both of which sign and verify emails using digital signatures and DNS records. Mail-DKIM can be used by any Perl program that wants to provide support for DKIM and/or DomainKeys.

The osmtpd API is an event-based C programming interface for writing OpenSMTPd filters.

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.

Email::Address::XS implements RFC 5322 parser and formatter of email addresses and groups. Unlike Email::Address, this module does not use regular expressions for parsing but instead is implemented in XS and uses shared code from Dovecot IMAP server.

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

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.

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

The l2md command line tool imports public-inbox archives via Git and exports them in maildir format or to an MDA through a pipe.

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.

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.

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.

Nullmailer is a simple replacement MTA for hosts that receive no local mail and only relay mail to a fixed set of smart relays. It's useful for systems such as Web servers that must be able to send email notifications, without having to run a full-blown MTA such as sendmail or qmail.

Nullmailer is designed to be simple to configure, easy to extend, and secure. It requires little ongoing administration. The included sendmail emulator front-end should allow most (if not all) sendmail-compatible programs to run without any changes.

Email::Simple provides simple parsing of RFC 2822 message format and headers.

Pigeonhole adds support for the Sieve language (RFC 5228) and the ManageSieve protocol (RFC 5804) to the Dovecot e-mail server.

Sieve is a language for filtering incoming mail. Messages can be forwarded or sorted into separate folders. Unwanted messages can be rejected or discarded, and, when the user is not available, the Sieve interpreter can send an automated reply.

Sieve is meant to be simple, extensible, and system-independent. The intention is to make it impossible to write anything more complex (and dangerous) than simple mail filters. Unlike most other mail filtering script languages, Sieve does not allow users to execute arbitrary programmes.

Through the ManageSieve protocol, users can remotely manage their Sieve scripts without needing file system access. The server accepts only valid scripts to prevent embarrassing errors later on.

notifymuch displays desktop notifications for messages in the notmuch database. The notifications are sent using libnotify to a notification daemon. The query to find messages to send a notification about is configurable, and a notification for the same message will not be send within a configurable period (defaults to 48 hours). To use notifymuch, run notifymuch after new mail is indexed, this can be automated by invoking notifymuch from the post-new hook.

libESMTP is an SMTP client that manages posting (or submission of) electronic mail via a preconfigured MTA.

It may be used as part of a MUA, or other program that must be able to post electronic mail where mail functionality may not be that program's primary purpose.

libESMTP's high-level API shields developers from the complexity of SMTP. It transparently handles many SMTP extensions including authentication, TLS, and PIPELINING for performance. Even without a pipelining server, libESMTP offers much better performance than would be expected from a simple client.

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.

This package implements a functionality to translate standard protocols (SMTP, IMAP, CardDAV) into ProtonMail API requests.

This is an address lookup tool using a Notmuch database, useful for email address completion.

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.

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.

This is a Python library for the generation of email authentication headers. The library can perform DKIM, SPF, and DMARC validation, and the results are packaged into the Authentication-Results header. The library can DKIM and ARC sign messages and output the corresponding signature headers.

The purpose of this mail library is to provide a portable, efficient framework for different kinds of mail access: IMAP, SMTP, POP and NNTP. It provides an API for C language. It's the low-level API used by MailCore and MailCore 2.