[Dovecot] NTLM authentication does not work

[Alexander Cherniak]

Dear Experts,
I configured Samba, Kerberos, etc., can login to my CentOS using ADS account, but missing something in my Dovecot config.

Windbind seems to work:
 [root at aCentOs2 dovecot]# wbinfo -a wAlex%pass
 plaintext password authentication succeeded
 challenge/response password authentication succeeded

Same is true for ntlm_auth helper:
 [root at aCentOs2 dovecot]# /usr/bin/ntlm_auth --username=wAlex --password=pass
 NT_STATUS_OK: Success (0x0)

But I couldn't get into Dovecot (with or without auth_use_winbind option):
. login wAlex pass
. NO [ALERT] Unsupported authentication mechanism.

Despite very verbose logging, there no clues there. Bellow's my dovecot -n output:

# 2.0.0: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.18-194.11.1.el5 i686 CentOS release 5.5 (Final)
auth_debug = yes
auth_debug_passwords = yes
auth_master_user_separator = *
auth_mechanisms = ntlm
auth_use_winbind = yes
auth_verbose = yes
auth_verbose_passwords = plain
debug_log_path = /var/log/Dovecot/dovecot_debug.log
disable_plaintext_auth = no
info_log_path = /var/log/Dovecot/dovecot_info.log
log_path = /var/log/Dovecot/dovecot.log
mail_location = maildir:~/Maildir
protocols = imap
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
userdb {
  args = uid=vmail gid=vmail home=/home/vmail/%u allow_all_users=yes
  driver = static
}

It might be irrelevant, but although the lines "auth_use_winbind = yes" and "auth_winbind_helper_path = /usr/bin/ntlm_auth" are close together in the config file, I cannot see the latter when run dovecot -n.

I am quite new to Dovecot and will appreciate any help.
Thanks, Alex.