mail/dovecot/10-logging.conf

log_path = /dev/stdout

#auth_verbose = yes

plugin {
  # Events to log. Also available: flag_change append
  #mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
  # Available fields: uid, box, msgid, from, subject, size, vsize, flags
  # size and vsize are available only for expunge and copy events.
  #mail_log_fields = uid box msgid size
}