> Why do you ask? It's much easier for old school non web 2.0 people to use mbox or maildir text versions.. load the whole thing up in mutt or whatever. The main benefit is being able to search using search tools you know work for you across all your mail. Mutt, subject, sender, regex, perl, etc. Hitting reply actually works :) Online web stuff is meant for kids and a real pain at that, and if search is provided, it's pretty limited.
As to boldly going where few have gone before... The FreeBSD project has it's entire mail archives available... about 16 years and gigs worth, raw as delivered... via ftp and cvsup. It's fantastic. No worries about dropped mail or bouncing oneself off the list due to your mail provider failing to have a clue. With some scripts, it's great for historical search and daily use. And it integrates into well designed mirroring/distribution pretty easily. Also interesting: markmail.org I might suggest something like that. Split mbox by month, gzip prior months, current month as a raw live mbox. Rsync will do its efficient append mode thing on it for mirroring, etc. As to spam... There's really no point in attempting to hide addresses/headers in this fashion. Just as how marc, gmane, etc subscribe to lists, so do spammers. They're not dumb, they know subscribing yields a goldmine. People's machines get hacked and any 'private' contact list gets sent out to botnets. Or they import you into social network sites. The only place spamfighting makes sense these days is at the mta layer and post mta off in userland somewhere.