RFC 2822 has been superceded:

http://www.rfc-editor.org/rfc/rfc5322.txt

Since you apparently use
ikiwiki, you might be interested in the mailbox plugin that I wrote

http://pivot.cs.unb.ca/git/?p=ikimailbox.git;a=summary

I’ll be the first to admit that it is immature. But it is small (1.1 millimhonarc) and deals with threading. It could be somewhere to start.

There’s also mod_mbox from apache:
http://httpd.apache.org/mod_mbox/

…which sucks (there’s no search, no way to link to a thread rather than a message, browsing from message view to its thread loses context, etc). For a while some of the projects there used eyebrowse:

http://eyebrowse.tigris.org/

…which sucks harder – mails kept going missing from its index before apache abandoned it.

• Sympa - A product developed by French at the start.
• SWAML not tested
• Communigate - not tested
• RESTmail - not strictly what you are looking for, but another way of thinking about it.

Another issue once, it has been archived on the Web… Search engine for mail data.

• MASE W3C version done by Olivier Théreaux and Eric Prud'hommeaux.

Maybe a good way to think about that issue is not that much a Web archive, but more about dynamic views of the mails. Example: Show me this mailing-list, Show me the thread of this discussions. etc. (ala Spotlight in Mail.app) Then we enter into performance, caching issues

#!/bin/bash

export HM_SHOWHTML=1
export HM_LINKQUOTES=1
export HM_SHOWHEADERS=1
export HM_DEFAULTINDEX="thread"
for i in ~/Mail/*/
do

        LABEL=$(basename $i)
        WWWDIR=/srv/www/archive.dabase.com/$LABEL

        for mail in $i/cur/*
        do
                echo $mail
                hypermail -L en -l $LABEL -i -u -d $WWWDIR < $mail
        done


done

sudo chown hendry:www-data -R $WWWDIR