[Dovecot] problem with disable_plaintext_auth

[Olivier Nicole]

Hi,

I am using dovecot with postfix for authentication.

Everything (TLS/SSL, authentication) is working fine, except that when
I set:

    disable_plaintext_auth = yes

I still can authenticate with plain text on a no TLS/SSL session:

    20 mail2.cs.ait.ac.th ESMTP Postfix (2.6.2)
    EHLO [192.41.170.57]
    250-mail2.cs.ait.ac.th
    250-PIPELINING
    250-SIZE 10240000
    250-VRFY
    250-ETRN
    250-STARTTLS
    250-AUTH PLAIN LOGIN
    250-AUTH=PLAIN LOGIN
    250-ENHANCEDSTATUSCODES
    250-8BITMIME
    250 DSN
    AUTH PLAIN XXXX
    235 2.7.0 Authentication successful
    
My dovecot configuration is:

    # 1.1.16: /usr/local/etc/dovecot.conf
    # OS: FreeBSD 7.2-RELEASE-p2 amd64  
    base_dir: /var/run/dovecot/
    protocols: none
    ssl_listen: *
    ssl_ca_file: /usr/local/ssl/ca/ait-itserv.crt
    ssl_cert_file: /usr/local/ssl/crt/mail2.cs.ait.ac.th.crt
    ssl_key_file: /usr/local/ssl/key/mail2.cs.ait.ac.th.key
    ssl_cipher_list: ALL:!LOW:!SSLv2
    login_dir: /var/run/dovecot/login
    login_executable: /usr/local/libexec/dovecot/imap-login
    login_chroot: no
    login_greeting_capability: yes
    verbose_proctitle: yes
    first_valid_uid: 1000
    first_valid_gid: 1000
    mail_privileged_group: mail
    mail_location: mbox:~/mail/:INBOX=/var/mail/%u
    imap_client_workarounds: delay-newmail netscape-eoh tb-extra-mailbox-sep
    auth default:
      mechanisms: plain login
      username_format: %Ln
      verbose: yes
      debug: yes
      passdb:
        driver: ldap
        args: /usr/local/etc/dovecot-ldap.conf
      passdb:
        driver: passwd
        args: blocking=yes
      socket:
        type: listen
        client:
          path: /var/spool/postfix/private/auth
          mode: 432
          user: postfix
          group: postfix
        master:
          path: /var/run/dovecot/auth-master
          mode: 384
    
Any help is welcome.

Best regards,

Olivier