[Dovecot] hunting timeouts

Hi guys,

I inherited a Dovecot 1.0.1, which I will have to upgrade, but until then I need, if possible, to resolve a timeout.

• we have about 25 IMAP users
• the busiest user has about 100 000 messages (Maildir) in less than 100 folders
• the mail server is on HP server with server grade 2.5" HDDs in RAID 5
• the load average of the server is low (the 5/15 minute is under 0.20)
• the mail server is in-house on Gigabit Ethernet

The timeout we face is that sometimes even small messages take 20-40 seconds to open (i. e. Tunderbird 2 on Windows 7). Or connection to the mail server timeouts.

Could you give me a few tips where can I look in order to detect the possible reason for these timeouts.

Thank you, Iv