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

[Root Kev]

Hello all,

We have put Dovecot 2.1.4 on several of our production servers (CentOS, on
Dell R710, with 20GB memory, dual CPU Quad-core). We have a single instance
of Dovecot running and currently have several instances of Popa3d.  When
there are significant amount of popping from 2 mailboxes that dovecot that
is popping from (500+ msgs in the mailboxes), the popping of the messages
causes the boxes to become unresponsive.  We use another application that
connects to the Dovecot, downloads 2-10 messages, then processes them, then
sends the delete command to Dovecot.

When this issue occurs we are unable to become Root, or login again if we
close our ssh connection.  This only occures when Dovecot is doing the
popping.  If we only run the older Popa3d, this doesn't occur.  We believe
it is caused by the way dovecot is authenticating.

We are using auth_mechanisms = plain

passdb
drive = shadow

usedb
driver = passwd
args = blocking=yes

If anyone could suggest what could be causing the login issue, we would
appreciate any incite to fix it!

Thanks,

Kevin