bottle.py
=========
Bottle is a fast, simple and lightweight WSGI micro web-framework for
Python. It is distributed as a single file module and has no
dependencies other than the Python Standard Library.

dkimpy
======
Python module that implements DKIM (DomainKeys Identified Mail) email
signing and verification (RFC6376). It also provides helper scripts for
command line signing and verification. As of 0.7.0 it supports DKIM
signing/verifying of ed25519-sha256 signatures (RFC 8463). As of
version 0.9.0, it also supports the RFC 8617 Authenticated Received
Chain (ARC) protocol.

fdm
===
fdm is a program designed to fetch mail from POP3 or IMAP servers, or
receive local mail from stdin, and deliver it in various ways.
    https://github.com/nicm/fdm

fetchmail
=========
Fetchmail is a full-featured, robust, well-documented remote-mail
retrieval and forwarding utility intended to be used over on-demand
TCP/IP links (such as SLIP or PPP connections). It supports every
remote-mail protocol now in use on the Internet: POP2, POP3, RPOP,
APOP, KPOP, all flavors of IMAP, ETRN, and ODMR. It can even support
IPv6 and IPSEC.

pwd.sh
======
pwd.sh is a Bash shell script to manage passwords and other secrets.
It uses GnuPG to symmetrically (i.e., using a master password) encrypt
and decrypt plain text files.
drduh/Purse is a fork which uses public key authentication instead of a 
master password and can integrate with YubiKey. 
    https://github.com/drduh/pwd.sh
    
mpop
====
mpop is a POP3 client: it retrieves mail from POP3 mailboxes.

Features include:
Support for multiple accounts
Header based mail filtering: filter junk mail before downloading it
Delivery to mbox files, maildir folders, or a mail delivery agent (MDA)
TLS support including client certificates
Many authentication methods
Support for Internationalized Domain Names (IDN)
Fast POP3 implementation using command pipelining
SOCKS proxy support
    https://marlam.de/mpop/
    
mairix
======
mairix is a program for indexing and searching email messages stored in
Maildir, MH or mbox folders
    https://github.com/vandry/mairix
    
libopensmtpd & filter-dkimsign
==============================
These are to enable opensmtpd to dkim sign messages. On Debian 10, do
this:

# apt install libevent-dev libssl-dev mandoc
libopensmptd# make -f Makefile.gnu
libopensmptd# make -f Makefile.gnu install

then same as above in filter-dkimsign directory.

S-nail
======
S-nail provides a simple and friendly environment for sending and
receiving mail. It is intended to provide the functionality of the
POSIX ∞ mailx(1) (∞ Wikipedia) command, but is MIME capable and
optionally offers extensions for line editing, S/MIME, SMTP and POP3,
among others. It divides incoming mail into its constituent messages
and allows the user to deal with them in any order. [Image: S-mailx
heraldic animal]It offers many COMMANDS and INTERNAL VARIABLES for
manipulating messages and sending mail. It provides the user simple
editing capabilities to ease the composition of outgoing messages, as
well as providing the ability to define and send to names which address
groups of users, and increasingly powerful and reliable non-interactive
scripting capabilities.

https://www.sdaoden.eu/code.html

mailsend
========
A program to send mail via SMTP from command line

    https://github.com/muquit/mailsend