I've kept most of the e-mail I've sent and received since 1984. (yes, that's '84, and that's not a typo.) It's several hundred megabytes in size
It's all indexed with AskSam (www.asksam.com), and I can zone in on any message by keyword, sender, etc....much more rapidly that waiting for some Java process and HTML screens to redraw.
I've written articles about it at :
It's a very powerful tool, for contact management, research, and just simply disarming people. ("No, you didn't say that in 1987, see, you're contradicting yourself!)