[exim] selective greylisting

Hi,

in my smtp server, I want to do selective greylisting.
This means, that I am greylisting every mail, which has to
high spam score. I am using greylistd
For this, I have the following rule in my acl_smpt_data:

  defer
    message     = $sender_host_address is not yet authorized to deliver mail \
                  from <$sender_address> to <$local_part@$domain>. \
                  Please try later.
    log_message = greylisted (<$sender_address> -> <$local_part@$domain>)
    condition   = ${if >{$spam_score_int}{${eval:60-$acl_m_spamvalue}}{true}{false}}
    add_header  = X-Spam-Extra: Doing greylisting
    set acl_m9  = $sender_host_address $sender_address $local_part@$domain
    set acl_m9  = ${readsocket{/var/run/greylistd/socket}{$acl_m9}{5s}{}{}}
    condition   = ${if eq {$acl_m9}{grey}{true}{false}}

I notice the following problems:
1. $local_part and $domain do not seem to be set. Is this normal for acl_smtp_data lists? How can I get them?
2. some senders (like googlemail) always change there $sender_host_address and by that do not get through.
I could remove the sender_hist_address complete, or I could add sender_helo_name.

Can the sender_helo_name change for every atemp?

Thanks!
Nathan