acl_check_rcpt:

defer message = $sender_host_address is not yet authorized to deliver \
                   mail from <$sender_address> to <$local_part@$domain>. \
                   Please try again in a few minutes.
log_message   = greylisted.
   !senders      = :
   !hosts        = : +relay_from_hosts : \
                     ${if exists {/etc/greylistd/whitelist-hosts} \
                                 {/etc/greylistd/whitelist-hosts}{}} : \
                     ${if exists {/var/lib/greylistd/whitelist-hosts} \
                                 {/var/lib/greylistd/whitelist-hosts}{}}
   !authenticated = *
   domains        = +local_domains : +relay_to_domains
   verify         = recipient/callout=20s,use_sender,defer_ok
   condition      = ${readsocket{/var/run/greylistd/socket} \
                    {--grey \
                    $sender_host_address \
                    $sender_address \
                    $local_part@$domain} \
                    {5s}{}{false}}

  # Accept if the source is local SMTP (i.e. not over TCP/IP). We do this by
  # testing for an empty sending host field.

  accept  hosts = :