[Dovecot] outlook 2007 very slow.

Hello

I have a user with 2500+ sub folders. Total mailboxes size is around 6G. (mdbox, dovecot 2:2.0.14)

Syncing/Receiving appears to be slow, with outlook 2007. He does not want to switch to an alternative, due to various reasons.

I did not find any error logs indicate issues.

during idle, imap process appears to loop at adding inotify watches to all folders.

I found outlook-idle in wiki, but it is obsolete.

doveconf: Warning: Obsolete setting in /etc/dovecot/conf.d/20-imap.conf:55: imap_client_workarounds=outlook-idle is no longer necessary

Any one else having similar issue? Anything else I should do to narrow down the issue?

Thanks KuiZ