Add "Using Traditional Unix Mail Program" section to email.md

This patch is provided to Tilde.club under the terms of
GNU General Public License, any version
published by the Free Software Foundation.

wiki/source/email.md

@@ -6,7 +6,7 @@ author:
 category: tutorial
 ---
 
-Your shiny, new tilde.club account comes with an email account. `alpine`  is a command-line email application to use it, as is `mutt`. Good old-fashioned `mail` works too, although it's a little cryptic.
+Your shiny, new tilde.club account comes with an email account. `alpine`  is a command-line email application to use it, as is `mutt`. [Good old-fashioned `mail` works too](#using-traditional-unix-mail-program), once configured properly; although it's a little cryptic.
 
 `alpine` is menu driven, and the menus are self-explanatory; it's surprisingly easy to learn, and surprisingly powerful when you want to customize it.
 
@@ -121,6 +121,75 @@ those emails would not produce notification.
 where people write Sieve filter
 to redirect unsolicited emails into <q>Junk</q> folder)
 
+## Using Traditional Unix Mail Program
+
+A traditional Unix `mail` program provided on Tilde.club
+is [Heirloom Mailx](https://heirloom.sourceforge.net/mailx.html).
+In its default configuration,
+it works for sending emails,
+but not receiving;
+due to the incoming [mailbox format](#mailbox-format)
+used in Tilde.club
+not being the old style system-wide centralized inbox folders
+used in the olden days,
+which the program expects by default.
+
+However,
+for anyone who are soughting for a traditional Unix mail experience,
+or is experimenting with Tilde.club using a real teleprinter;
+Heirloom Mailx could be configured
+to operate directly on your Tilde.club mailbox,
+with some quirks,
+by adding the following lines to your `~/.mailrc`
+or create it with the following lines if not already existing
+(substitute `USERNAME` part with your Tilde.club username):
+
+	set MAIL=/home/USERNAME/.mail
+	set folder=.mail
+	set emptybox
+	set newfolders=maildir
+	set record=+.sent-mail
+
+Once you did so,
+running `mail` would now show the list your emails
+if you have any in your inbox.
+(Type `q` and press <kbd>Enter</kbd> to quit)
+
+Tips:
+
+- Set your `PAGER` and `EDITOR` environment variables properly;
+	unless you really want to view your emails through `more`
+	and/or compose your emails through `ed`.
+	(Even if you are really using a teleprinter,
+	it is still a good idea to set these explicitly however)
+- Type `?` and press <kbd>Enter</kbd> for in-program help.
+	Also read a manual
+	(`man mail` from the main system command line).
+- Heirloom Mailx does not understand the Maildir++ subfolder structure;
+	so you will have to type the name of subdirectory
+	as seen in the filesystem
+	(including its dot prefix)
+	when changing folder.
+	For example,
+	use command:
+	
+		folder +.sent-mail
+	
+	to view the emails you have sent.
+	(See [mailbox format](#mailbox-format)
+	below for the default folders available)
+- When changing to view mail folder other than inbox,
+	you nearly always want to prefix it with `+`;
+	which means the folder is a subdirectory of the main email folder.
+- When changing to view the main inbox folder,
+	simply use `%` as folder name
+	without any prefix.
+- Marking email as junk here
+	does not do a thing you would normally expect
+	from modern email clients
+	or webmails;
+	so don't do it.
+
 ## Mailbox Format
 
 Tilde.club uses [Dovecot](https://www.dovecot.org/) as a local mail delivery agent