[Dovecot] Best small server config

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Hi,

Busy with dovecot on a linux server with not very much RAM in it (512
MB max total).

On this server dovecot will only handle about 12 users,
with never more than 3 IMAP webmail users at a time,
and a maximum of 2 POP3 users at a time using it.

I'm going all secure later on, but first I would like your opinion on
what configuration best to use with, say, max 5 users busy at one time,
and have it use as little RAM and CPU as possible.
(Same machine is also running httpd, squirrelmail, php5, postfix,
clamd, clamsmtpd, sshd.)

Here's my  /etc/dovecot.conf  now:
#
protocols = imap pop3
imap_listen = *
pop3_listen = my.servers.ip.address (hidden for this list)
ssl_cert_file = /etc/ssl/certs/imapd.pem
ssl_key_file = /etc/ssl/private/imapd.pem
ssl_parameters_file = /var/run/dovecot/ssl-parameters.dat
ssl_parameters_regenerate = 320
login_dir = /var/run/dovecot-login
login = imap
login = pop3
default_mail_env = maildir:/home/%u/Maildir
mailbox_idle_check_interval = 40
mail_full_filesystem_access = yes
login_user = dovecot

login_process_size = 64
login_process_per_connection = no
login_processes_count = 4
login_max_processes_count = 4
login_max_logging_users = 5

max_mail_processes = 140

imap_process_size = 192
pop3_process_size = 64

first_valid_uid = 500
last_valid_uid = 520

mail_cache_fields = MessagePart

mbox_locks = fcntl
mbox_read_dotlock = no
mbox_lock_timeout = 380

auth = default
auth_mechanisms = plain
auth_userdb = passwd
auth_passdb = pam
auth_process_size = 64
auth_user = root
#

Any insight or advice welcomed!

Ben de G.