[Dovecot] Imap new messages listing is very slow with big meilbox - why?

[Mart Pirita]

Tere.

I had impression, that Dovecot does cache the Maildir status, new and 
old messages and so checking (finding the new messages) the new emails 
is fast. But what is the truth? Latelly noticed, that using latest 
Thunderbird, 1 mb line, osx or xp, imap and maildir, if mailbox includes 
for example about 30 000 messages Thunderbird's command "Get all new 
messages" takes more than a minute and with mobile device (Nokia E50, 
Profimail) about 5-7 minutes.

So I can log in and auth quick, I see that Inbox contains 30 000 
messages but then new messages listing (sorting the new messages from 
whole messages without actual headers download) takes forever.

Is this normal? How to speed it up? Is this email client or Dovecot issue?


Dovecot runs on customized RedHat, 2.6.19 kernel, with settings:

# 1.0.5: /etc/dovecot.conf
protocols: pop3 pop3s imaps
ssl_parameters_regenerate: 0
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
login_log_format_elements: %u [%r] %m %c
mail_location: maildir:~/Maildir
mmap_disable: yes
maildir_copy_with_hardlinks: yes
maildir_copy_preserve_filename: yes
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
imap_client_workarounds(default): outlook-idle netscape-eoh 
tb-extra-mailbox-sep delay-newmail
imap_client_workarounds(imap): outlook-idle netscape-eoh 
tb-extra-mailbox-sep delay-newmail
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
pop3_logout_format(default): top=%t/%p, retr=%r/%b, del=%d/%m, size=%s
pop3_logout_format(imap): top=%t/%p, retr=%r/%b, del=%d/%m, size=%s
pop3_logout_format(pop3): retr=%r/%R, del=%d/%m, size=%s
auth default:
  cache_size: 1024
  passdb:
    driver: pam
    args: cache_key=%u%r%s *
  userdb:
    driver: passwd


-- 
Mart