[Dovecot] Dovecot and Outlook Express "plaintext authentication not allowed..."

[D Chen]

Server: Ubuntu 11.10 server with postfix (MTA), dovecot (MDA)
Mail client: Outlook Express in Windows XP with IMAP on port 143, SMTP on port 25

When tried to set up a new Outlook Express mail acct, the following error encountered:

     Your IMAP server wishes to alert you to the following:
     plaintext authentication not allowed without SSL/TLS, but your client did it anyway.  If
     anyone was listening, the password was exposed.

When asked "would you like to download folders from the mail server you added?" then got the
following error:

The server has rejected your login.  Please verify that your user name and password are correct.

I re-entered several time with the correct username and password, but still responded the same error.

Any insights would be greatly appreciated.


Here is the message from the /var/log/mail.log:


Apr 17 01:54:17 server dovecot: imap-login: Disconnected (tried to use disabled plaintext auth): rip=
192.168.20.51, lip=192.168.20.100Apr 17 01:54:28 server dovecot: imap-login: Disconnected (tried to use disabled plaintext auth): rip=
192.168.20.51, lip=192.168.20.100

What might be wrong in my dovecot.conf file.  Below is my dovecot.conf file:

# 2.0.13: /etc/dovecot/dovecot.conf
# OS: Linux 3.0.0-16-server x86_64 Ubuntu 11.10 
log_timestamp = "%Y-%m-%d %H:%M:%S "
mail_location = maildir:~/Maildir
mail_privileged_group = mail
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date
passdb {
  driver = pam
}
passdb {
  driver = pam
}
plugin {
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
}
protocols = imap pop3 sieve
service auth {
  unix_listener /var/spool/postfix/private/auth-client {
    group = postfix
    mode = 0660
    user = postfix
  }
  unix_listener /var/spool/postfix/private/dovecot-auth {
    group = postfix
    mode = 0660
    user = postfix
  }
  user = root
}
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_cipher_list = ALL:!LOW:!SSLv2:ALL:!aNULL:!ADH:!eNULL:!EXP:RC4+RSA:+HIGH:+MEDIUM
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
  driver = passwd
}
userdb {
  driver = passwd
}
protocol imap {
  imap_client_workarounds = delay-newmail
  mail_max_userip_connections = 10
}
protocol pop3 {
  mail_max_userip_connections = 10
  pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
  pop3_uidl_format = %08Xu%08Xv
}
protocol lda {
  deliver_log_format = msgid=%m: %$
  mail_plugins = sieve
  postmaster_address = postmaster
  quota_full_tempfail = yes
  rejection_reason = Your message to <%t> was automatically rejected:%n%r
}