[Dovecot] High level of pop3 popping causing server to become unresponsive

[Thierry de Montaudry]

On 24 May 2012, at 16:54, Root Kev <root.kev at gmail.com> wrote:

> Currently cannot use IMAP as our application to access the mailbox
> currently is only setup to access pop3 mailboxes.  We are currently using
> Dovecot 2.1.4.  Below is the majority of our configs, it is mostly basic:
> 
> protocols = pop3
> listen = ***Address here***
> base_dir = /var/run/dovecot1/
> instance_name = Popper
> login_greeting = Popper
> mail_location =
> mbox:/var/empty:INBOX=/opt/mailstore/spool/mail/%u:INDEX=MEMORY
> 
> !include conf.d/*.conf
> !include_try local.conf
> 
> disable_plaintext_auth = no
> auth_mechanisms = plain
> log_path = syslog
> syslog_facility = mail
> auth_verbose = yes
> log_timestamp = "%b %d %H:%M:%S "
> namespace inbox {
> inbox = yes
> }
> mail_privileged_group = mail
> lock_method = fcntl
> mbox_read_locks = fcntl
> mbox_write_locks = dotlock fcntl
> pop3_uidl_format = %08Xu%08Xv
> passdb {
>  driver = checkpassword
>  args = /usr/bin/checkpassword
> }
> userdb {
>  driver = prefetch
> }

Hi,

Having a system with a third of our users on POP3 (2300000 of them), no trouble with dovecot (v2.1.5, on CentOS 5).
But one thing surprises me in your config, the INDEX=MEMORY in the location parameter. That means that for each POP3 connection, dovecot has to read each and every mails to create the index in memory. That might be why the machine becomes unresponsive.
Unless you have a specific reason to use memory index (and I would be curious to know about it), I would suggest to remove this and keep standard file indexes, and your performances should improve a lot.

Regards,

	Thierry