[Dovecot] /etc/passwd authentication: ERR authentication failed

Hi all, I am a newbie with dovecot. I have a problem with it's authentication. -I installed dovecot 1.0 beta3 at /usr/local/dovecot. -I want to use my linux system accounts with mail (authentication using /etc/passwd). -I have a user account: huytq with password: 123456 -dovecot is started ok. I used telnet to login:

        +OK Welcome LENSECAP HCM mail
         user huytq
        +OK
         pass 123456
         -ERR Authentication failed.

and this is the infolog file says: dovecot: Mar 18 22:26:50 Info: auth(default): client in: AUTH 1 PLAIN service=POP3 lip=192.168.1.254 rip=192.168.1.253 resp=<hidden> dovecot: Mar 18 22:26:50 Info: auth(default): passwd(huytq, 192.168.1.253): password mismatch dovecot: Mar 18 22:26:51 Info: auth(default): client out: FAIL 1 user=huytq dovecot: Mar 18 22:27:50 Info: pop3-login: Disconnected: Inactivity: user=<huytq>, method=PLAIN, rip=192.168.1.253, lip=192.168.1.254

This is my conf file:

###################### dovecot.conf ################################# base_dir = /opt/dovecot/ protocols = pop3 listen = 192.168.1.254

    ssl_disable = yes

    log_path = /usr/local/dovecot/log/log
    info_log_path = /usr/local/dovecot/log/infolog
    log_timestamp = "%b %d %H:%M:%S "

    disable_plaintext_auth = no
    auth_debug = yes
    auth_verbose = yes

auth default { mechanisms = plain passdb passwd { } userdb passwd { } user = root }

    login_dir = /opt/dovecot/login
    login_chroot = yes
    login_user = dovecot
    login_greeting = Welcome  QuocHuy mail server
    login_log_format_elements = user=<%u> homedir=%h  method=%m rip=%r

lip=%l %c login_log_format = %$: %s

    default_mail_env = maildir:/opt/mail_data/%u/Maildir

    mail_debug = yes

protocol pop3 { login_executable = /usr/local/dovecot/libexec/dovecot/pop3-login mail_executable = /usr/local/dovecot/libexec/dovecot/pop3 pop3_uidl_format = %v.%u } #########################################################

Any opinion? Thanks in advance.

Quoc Huy Trinh