dovecot 连接至 IMAP 服务器失败

Question

安装了post fix和dovecot，本地能收到cron的报错邮件，但imap连不上。
systemctl绿灯，lsof-i也是正确。

# telnet 127.0.0.1 143
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
Connection closed by foreign host.

各位能帮忙看看吗？

cat dovecot.conf
protocols = imap
mail_location = maildir:/var/vmail/%d/%n/Maildir

## uncomment this if you already have email from
## courier for instance.

#namespace private {
#  separator = .
#  prefix = INBOX.
#  inbox = yes
#}
## change section "protocol lda" to:
protocol lda {
  # Address to use when sending rejection mails.
  postmaster_address = [e-mail]
  log_path = /var/vmail/dovecot-deliver.log
  # Hostname to use in various parts of sent mails, eg. in Message-Id.
  # Default is the system's real hostname.
  #hostname =

  # Support for dynamically loadable plugins. mail_plugins is a space separated
  # list of plugins to load.
  #mail_plugins =
  #mail_plugin_dir = /usr/lib/dovecot/modules/lda

  # Binary to use for sending mails.
  #sendmail_path = /usr/lib/sendmail

  # UNIX socket path to master authentication server to find users.
  auth_socket_path = /var/run/dovecot/auth-master

  # Enabling Sieve plugin for server-side mail filtering
  # handy for storing spam in their folders
  mail_plugins = cmusieve
  #global_script_path = /var/vmail/globalsieverc
}                                                          

## in section auth default
## change :
auth_mechanisms = plain
#mechanisms = plain login
## comment out "passdb pam"
## and make sure the following is in
## to look for users in the DB
#  passdb sql {
    # Path for SQL configuration file, see /etc/dovecot/dovecot-sql.conf for example
 #   args = /etc/dovecot/dovecot-sql.conf
  #}

## and add this so dovecot does not deal with uid/gid
## we use uid and gid 5000 for everybody
  #userdb static {
  #  args = uid=5000 gid=5000 home=/home/vmail/%d/%n allow_all_users=yes
  #}

## next make sure the section "socket listen" looks like this
## so dovecot and postfix work happily together
 # socket listen {
  #   master {
   #    path = /var/run/dovecot/auth-master
      # mode = 0600
     #  user = vmail # User running Dovecot LDA
       #group = mail # Or alternatively mode 0660 + LDA user in this group
    # }
    # client {
      # The client socket is generally safe to export to everyone. Typical use                                              # is to export it to your SMTP server so it can do SMTP AUTH lookups
      # using it.
      #path = /var/spool/postfix/private/auth
      #path = /var/run/dovecot/auth-client
     # mode = 0660
   #   user = postfix
    #  group = postfix
  #   }
 #  }
passdb {
driver = sql
args = /etc/dovecot/dovecot-sql.conf
}