+<h2>procmail</h2>
+If you use procmail for your main mailbox, PLEASE, erase your .forward
+file and put a .procmailrc in its place instead. This feature has been
+supported on debian.org machines for a good while now, and will continue to be
+supported.
+
+<p>
+The correct way to invoke procmail for extension addresses is "|/usr/bin/procmail [options]"
+Ignore the IFS=".." stuff in the procmail man page.
+
+<h2>MailBox formats</h2>
+Emails can be saved to mailboxes or maildirs by using the correct lines in a
+.forward file:
+<p>
+Mailbox format files "/debian/home/foo/Mbox"
+<br>Maildir format files "/debian/home/foo/MDir/"
+
+<p>
+To deliver to /var/spool/mail/foo use a construct like '|/usr/bin/procmail
+-m /dev/null'. Putting the mailbox path will not work. You must use
+absolute paths for mailboxes, qmail-like ./ paths are not supported by
+Exim.
+
+<p>
+Also, 'Exim Filter' files are deliberately turned off.
+
+<h2>Delivey Environment</h2>
+Some environment variables are set per-message (not quoted! Carefull!)
+It is important to note that the environment variables dealing with
+addressing apply to the ENVELOPE address are are totally completely
+unrelated to the actual contents of the message:
+<p>
+'Standard' Env Variables:
+<ol>
+<li>EXTENSION (the 'foo' in .forward-foo)
+<li>LOGNAME,USER (your user name)
+<li>SENDER (envelope originator of message)
+</ol>
+
+<p>
+'Qmail' Env Variables:
+<ol>
+<li>EXT == EXTENSION
+<li>LOCAL = (the entire bit before the @)
+<li>RECIPIENT = (the entire envelope to)
+</ol>
+
+<p>
+Such that, <i>$RECIPIENT = $LOCAL-EXTENSION@<something></i>.
+