vertual users in mail server

[all2dark]

I am having CentOS 4.4 server installed sendmail ,dovecot and DNS (namd) working fine of test domain in my office. All are default configuratons and working fine for 79 email accounts as system users with no login shell.

I need to configure dovecot each system user as virtual user for first part and need to set various size of email boxes of each user. So I have removed default dovecot and compiled from source to accomplish my goal.

My dovecot config file is at /usr/local/etc/dovecot.conf shown bellow.

# Dovecot configuration file
base_dir=/usr/local/var/run/
protocols = imap
listen = *:143
# We can use plain text passwords
disable_plaintext_auth = no
# Logging
log_path = /var/log/dovecot.log
info_log_path = /var/log/dovecot.info.log
log_timestamp = "%b %d %H:%M:%S "
# SSL settings
# Without ssl
ssl_disable = yes
# Login processes
login_user = dovecot
login_greeting = Hi buddy, have an account ?
login_log_format = %$: %s
# Mailbox locations and namespaces
mail_extra_groups = mail
# Mailbox locations and namespaces
# Clients Inbox at /var/mail, Clients Folders at /var/mail/folders/username/
mail_location = mbox:/var/mail/folders/%u/:INBOX=/var/mail/%u
# Mail processes
mail_debug = yes
mail_log_prefix = "%Us(%u): "
verbose_proctitle = yes
first_valid_uid = 1000
last_valid_uid = 5000
max_mail_processes = 2048
# mbox-specific settings
mbox_read_locks = dotlock fcntl
mbox_write_locks = dotlock fcntl
# IMAP specific settings
protocol imap {
}
# LDA specific settings
protocol lda {
postmaster_address = root@mydomain.org
hostname = mydomain.org
# Sieve plugin for local delivery agent
mail_plugins = cmusieve
log_path = /var/log/dovecot-local-deliver.log
auth_socket_path = /usr/local/var/run/dovecot-auth-master
}
# Authentication processes
auth_verbose = yes
auth_debug = yes
auth_debug_passwords = yes
auth default {
mechanisms = plain
passdb passwd-file {
# Virtual Users from file
args = /usr/local/etc/dovecot.passdb
}
userdb passwd-file {
# Virtual Users from file
args = /usr/local/etc/dovecot.passdb
}
user = root
# It's possible to export the authentication interface to other programs:
# For example getmail with MDA external
socket listen {
master {
path = /usr/local/var/run/dovecot-auth-master
mode = 0660
user = dovecot
group = mail
}
}
}

Mail authentication is done by file at same directory dovecot.passdb
Code:

user1:{PLAIN}pass1:1001:1001:User 1 Name:/var/mail/folders/user1
user2:{PLAIN}pass2:1002:1002:User 2 Name:/var/mail/folders/user2
user3:{PLAIN}pass3:1003:1003:User 3 Name:/var/mail/folders/user3
user4:{PLAIN}pass4:1004:1004:User 4 Name:/var/mail/folders/user4

Finally I can telnet to both dovecot IMAP and sendmail smtp servers and log r using outlook express to CentOS server. When I trying to send email to server using out look it gives error
Code:

The message could not be sent because one of the recipients was rejected by the server.
The rejected e-mail address was 'user1@elephent.lk'. Subject 'test',
Account: '192.168.1.1', Server: '192.168.1.1', Protocol: SMTP, Server Response:
'550 5.1.1 <user1@elephent.lk>... User unknown', Port: 25, Secure(SSL):
No, Server Error: 550, Error Number: 0x800CCC79

What will be the error ?

Or

Pls give me any good guide(url) to configure virtual users using dovecot ?
__________________
LASANTHA