This project is mostly defunct, but I would like to keep a record of it since it was one of my very first open source projects back in 2003! It was very relevant when I ran my own mailserver and checked mail using mutt directly on that mailserver.
Maildirtree is a simple program designed to look like tree(1). It displays hierarchies from a flat Maildir structure in the Courier style (that is, subfolders are named .Folder.Subfolder.) It displays a full count of messages, the number of unread messages and can be told to only provide a summary of the statistics thereof.
Currently, it ONLY supports Courier-style Maildir hierarchies; recursion and the tree format will not work quite right for other types of hierarchies.
Maildirtree is written in about 500 lines of C and was the object of an autoconf experiment. Therefore, the build process is somewhat overkill for such a small program, but it works nonetheless.
Some example output from Maildirtree (abridged from my own Maildir):
Maildir (0/20)
|-- Administrivia (0/15)
|-- DebianBugs (0/459)
|-- Drafts (0/0)
|-- Family (0/49)
|-- Friends (0/8)
|-- Junk Mail (109/109)
|-- Linux (0/0)
| |-- [debian-d-a] (0/4)
| |-- [debian-devel-changes] (2/2)
| |-- [debian-devel] (0/521)
| |-- [debian-mentors] (2/68)
| |-- [hybrid] (0/4)
| |-- [ircd-coders] (0/7)
| |-- [linux-kernel] (0/540)
| |-- [linux-mm] (0/998)
| `-- [sparclinux] (0/426)
|-- Sent Items (0/626)
|-- Stanford (0/72)
|-- Trash Can (0/0)
`-- Archive (0/0)
113 messages unread in 3 folders, 4808 messages total.
And in its 'summary' mode:
Maildir: 37 messages unread in 8 folders, 4003 messages total.
Unread messages in: Maildir, Linux/[d-i-cvs], Linux/[debian-d-a], Linux/[ircd-coders],
Linux/[irssi-users], Linux/[sparclinux], Linux/[hostap], Spam
Maildirtree is software released under the terms of the GNU General Public License, version 2.
I welcome any feedback to Maildirtree by email: joshk@triplehelix.org.