[Dovecot] EXPUNGE delay

[Eugene]

Hi people!

I just switched one of my servers from Courier to Dovecot. Planned to do it
anyway but had to do it faster after the discovery that courier [the version
I had installed, at least] returns malformed headers for a few messages,
causing Outlook Express to completely ignore them. Curiously, they were
visible in Squirrelmail and Nokia Series60 e-mail client.

Overal I am quite happy but have one little problem. More often than not, I
have to press 'Purge' button two or more times in order to actually remove
the deleted messages. The fragment of Outlook's IMAP log is below. 
Interestingly, Dovecot 1.0.7 (on another server) does not have such problem.

Best wishes
Eugene

IMAP: 00:46:56 [tx] 0yc9 UID STORE 172903 +FLAGS.SILENT (\Deleted \Seen)
IMAP: 00:46:56 [rx] 0yc9 OK Store completed.
IMAP: 00:46:58 [tx] 623w EXPUNGE
IMAP: 00:46:58 [rx] * 102 FETCH (FLAGS (\Deleted \Seen))
IMAP: 00:46:58 [rx] 623w OK Expunge completed.
IMAP: 00:46:58 [tx] 62lg IDLE
IMAP: 00:46:58 [rx] + idling
IMAP: 00:47:02 [tx] DONE
IMAP: 00:47:02 [rx] 62lg OK Idle completed.
IMAP: 00:47:02 [tx] a4si EXPUNGE
IMAP: 00:47:02 [rx] * 102 EXPUNGE
IMAP: 00:47:02 [rx] a4si OK Expunge completed.

dovecot version: 1.0.10
OS:  FreeBSD 5.3-RELEASE i386
dovecot -n
# 1.0.10: /usr/contrib/etc/dovecot.conf
base_dir: /var/run/dovecot/
protocols: imap imaps pop3 pop3s
ssl_cert_file: /etc/ssl/certs/xxxx.pem
ssl_key_file: /etc/ssl/private/xxxx.pem
disable_plaintext_auth: no
login_dir: /var/run/dovecot//login
login_executable(default): /usr/contrib/libexec/dovecot/imap-login
login_executable(imap): /usr/contrib/libexec/dovecot/imap-login
login_executable(pop3): /usr/contrib/libexec/dovecot/pop3-login
verbose_proctitle: yes
first_valid_gid: 0
mail_extra_groups: mail
mail_location: maildir:/home/%u/Maildir
mail_executable(default): /usr/contrib/libexec/dovecot/imap
mail_executable(imap): /usr/contrib/libexec/dovecot/imap
mail_executable(pop3): /usr/contrib/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/contrib/lib/dovecot/imap
mail_plugin_dir(imap): /usr/contrib/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/contrib/lib/dovecot/pop3
imap_client_workarounds(default): delay-newmail outlook-idle netscape-eoh
tb-extra-mailbox-sep
imap_client_workarounds(imap): delay-newmail outlook-idle netscape-eoh
tb-extra-mailbox-sep
imap_client_workarounds(pop3): outlook-idle
pop3_uidl_format(default):
pop3_uidl_format(imap):
pop3_uidl_format(pop3): %08Xu%08Xv
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd