[exim] Can't get spam acl to work.

Hi all.

I'm trying to get my system to use spamassassin with exim 4.62.

I've read the spect at:
http://www.exim.org/exim-html-4.62/doc/html/spec_html/ch40.html

And I STILL can't get this to work. All I want to do, for now, is add a
header to incoming mail that has the spam score. Since I've seen examples
that put this logic in two different acl's, I put it in both. Here is a
snippet from /etc/exim/exim.conf:

=======================================
begin acl

acl_smtp_data:
warn spam      = nobody:true
message   = X-Spam_score: $spam_score

acl_check_content:
warn spam      = nobody:true
message   = X-Spam_score: $spam_score

=======================================

When I receive a new email, the header isn't inserted. I see nothing added
to /var/log/email.log. Nothing that indicates that spamd was consulted is
printed into /var/log/exim/exim_main.log. I've verified that spamd is
running on 127.0.0.1:783.

What am I missing? And which acl should contain this logic?

Thanx in advance,
Mike.