Several bugfixes since 0.99.6rc3. Here's again the change summary since 0.99.5:

v0.99.6 2003-01-13 Timo Sirainen <tss@iki.fi>

+ THREAD=REFERENCES extension support. ORDEREDSUBJECT would be easy to
  add, but I think it's pretty useless.
+ SORT is much faster now.
+ mbox: If ~/mail directory isn't found, create it.
+ Log login usernames
* Some coding style changes (less typedefs)
- Mails with nested MIME parts might have caused incorrect BODY and
  BODYSTRUCTURE fetches and sometimes might have crashed dovecot
  (assert at imap-bodystructure.c). If client had already successfully
  done the BODY fetching a couple of times, the bug couldn't happen
  anymore since Dovecot then began caching the BODY data. So, this
  mostly happened with new users.
- non-UID SEARCH might gave wrong replies in certain conditions.
- SORT replied always with UIDs instead of sequences.
- If authentication was aborted by client ("*" reply to AUTHENTICATE),
  the login process crashed later.
- STATUS command gave invalid reply for mailboxes with spaces in name
- Timezones were parsed wrong with message dates
- Digest-MD5: We used "qop-options" instead of "qop", which was
  incompatible with at least Cyrus SASL.
- Realms in passwd-file were buggy
- Literals didn't work when logging in
- Crashed if it had to wait for mbox lock
- With invalid configuration auth and login processes were just dying
  and master filling log files infinitely.
- We didn't work with some 64bit systems