[Dovecot] POP3 Dovecot Auth CPU usage 75%+

[Root Kev]

Hello all,

I hope someone can help me, I have been testing out Dovecot to switch from
popa3d which I use at the moment.  When I get several users connecting and
disconnection multiple times, the Dovecot process with command Auth uses
50-90% of the CPU for the period which they are connecting.  I am wondering
if there is something that I may have misconfigured, or if there is
something that I can change so that this spike doesn't occur.

If anyone could shed some light on the issue, I would appreciate it,

Kevin

/var/mail# dovecot -n
# 2.1.4: /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-33-generic-pae i686 Ubuntu 10.04.4 LTS ext4
auth_cache_size = 10 M
auth_verbose = yes
disable_plaintext_auth = no
instance_name = Mail Popper 1
listen = 172.20.20.222
login_greeting = Mail Popper 1 Ready
mail_location = mbox:/var/empty:INBOX=/var/mail/%u:INDEX=MEMORY
mail_privileged_group = mail
namespace inbox {
  inbox = yes
  location =
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix =
}
passdb {
  driver = shadow
}
protocols = pop3
service pop3-login {
  service_count = 0
}
ssl = no
userdb {
  driver = passwd
}
protocol pop3 {
  pop3_uidl_format = %08Xu%08Xv
}