Selected section of /etc/exim4/exim4.conf.template configuration file:

  # acl_check_rcpt section

  # ***
  #   deny blacklisted recipients
  #   CONFDIR/local_recipient_blacklist holds a list of email addresses that should
  #   no longer have email accepted for them, but which need to be blocked explicitly
  #   due to wildcard email addresses being used that would normally accept the
  #   addresses.  Incoming messages with these recipients are blocked at RCPT time.
  # ***
  deny
    domains = +blacklist_filecheck_domains
    message = unknown user (error y1)
    condition = ${lookup{$local_part@$domain}\
        nwildlsearch\
        {yes}{no}}
    log_message = Address blocked (yee1)

  # ***
  #   Relay only recipients found in recipient_relay_lists
  # ***
  #
  deny
    domains = +rcpt_checked_relay_domains
    message = unknown user (error y2)
    !condition = ${lookup{$local_part@$domain}\
        nwildlsearch\
        {yes}{no}}
    log_message = Address unknown (yee2)