On Tue, 2009-10-13 at 11:37 -0700, Simon Gao wrote:

We have a few users experiencing locking problem. When starting Thunderbird, there is no new emails in Inbox. Dovecot createa a lock file /var/spool/mail/<user>.lock. It never completes openning Inbox. If closing the mail client, the open imap session does not get closed, nor the lock file get deleted.

What is the process doing? Check with "strace -p <imap process pid>"? How large is the user's mailbox?

Here are the errors in log:

dovecot: Oct 13 11:18:35 Warning: IMAP(user1): Our dotlock file /var/mail/user1.lock was deleted (kept it 88 secs) dovecot: Oct 13 11:18:35 Error: IMAP(user1): file_dotlock_delete() failed with mbox file /var/mail/user1: No such file or directory

I'd guess this is a huge mbox (or your disk I/O is very slow) and Dovecot takes a long time trying to read it. mbox_very_dirty_syncs=yes may be helpful.