$ cp dovecot.conf devecot.conf.org
$ vi dovecot.conf
$ diff devecot.conf.org dovecot.conf
24a25
> protocols = imap pop3
33a35
> base_dir = /var/run/dovecot/
$

# See also ssl=required setting.
#disable_plaintext_auth = yes
#20170406
disable_plaintext_auth = no

#log_path = syslog
#20180406
log_path = syslog

#syslog_facility = mail
#20180406
syslog_facility = mail

#mail_location =
#20180406
mail_location = maildir:~/Maildir

# SSL/TLS support: yes, no, required. <doc/wiki/SSL.txt>
#ssl = yes
ssl = no

#default_login_user = dovenull
#20180404
default_login_user = dovenull

#default_internal_user = dovecot
#20180406
default_internal_user = dovecot

service imap-login {
  inet_listener imap {
    #port = 143
#20180406
    port = 143

    service pop3-login {
  inet_listener pop3 {
    #port = 110
#20180406
    port = 110
  }

service submission-login {
  inet_listener submission {
    #port = 587
#20180406
    port = 587
  }
}