Chris Hastie speaks the gospel truth. People may know their email interface for daily reading of new mail, but probably not for archival browsing and searching! They're as well off using the Web for that "advanced" application as they are anything else.
What's more, many of the IMAP servers and clients I've used perform *terribly* when handed a truly huge folder. The thought of dozens or hundreds of archive users all trying to access one big folder at once is chilling. :) So you end up breaking into 2002/01, 2002/02, etc... and hope against hope that the client supports recursive searches (Mulberry, Mozilla and IE do not, last I checked).
