btree on disk

WA> It's also a fair assessment, I think, so say that it's a major
WA> pain that UW-IMAP doesn't support Maildir, and that a
WA> disinterested third party, with full view of all the other Unix
WA> software which supports Maildir (mutt, etc), would agree that
WA> the reticence is a bit puzzling. On _my_ system Maildir, with
WA> 20+ users, has proven far superior to mbox. But, for various
WA> reasons, I stick with UW-IMAP and mbox (for non-shell
WA> users), notwithstanding that the users who insist on keeping
WA> 10MB attachments in their folders continue to whine incessantly.

<URL:http://qmail.org./top.html#usersoft>
<URL:http://davideous.com./imap-maildir/>
<URL:http://greboguru.org./geek/qmail/>
<URL:ftp://ftp.cistron.nl/pub/people/miquels/imap/>

You can make it use Maildir format mailboxes if you want to.