My mail user agent is Astroid.

Behind the scenes, my email set up:

I use offlineimap to sync with my email server (running Kolab). My email is then indexed with Notmuch. Notmuch allows to tag and search emails (among many other useful things). I also use Afew, which helps by bringing some automation in email tagging (e.g. automatically tagging lists accordingly, learning to tag email over time which is useful to fight spam, etc.).

Overview

afew/	This is a tools that helps with automated 
└─ config   tagging of emails. 

astroid/	This is my mail user agent configuration (as a Git submodule)
├─ config           See https://github.com/hugoroy/.astroid
├─ hooks/		This is where I store astroid scripts.
|  └─ (+x) toggle
├─ keybindings	This is where I customize the astroid keybindings.
├─ (+x) poll.sh	This script syncs imap and tags incoming email.
├─ searches		This is where astroid stores saved queries and search history (not in a Git repo, obviously).
└─ ui		This is a symlink to the "ui/" directory in my customised UI branch of astroid (See <https://github.com/hugoroy/astroid/tree/ui>).

imap/	This is where I store my synced-imap maildirs (not in this Git repo)
├─ ampoliros
|	└─ ...
└─ archives/
└─ ...

netrc	This is where I store login info (not in this Git repo, obviously), see
		https://www.gnu.org/software/inetutils/manual/html_node/The-_002enetrc-file.html

	I created a symlink from ~/.netrc

notmuch/
├─ hooks/		I no longer use notmuch hooks. See `astroid/poll.sh`.
└─ notmuch-config

offlineimap/
├─ (+x) gnome-keyring-query.py
└─ offlineimaprc

signatures/	This is where I store my plain-text email signatures.
├─ perso.signature
└─ etc.signature