[exim] warn in acl doesn't give a log entry?

Hello,

I have the following lines in my exim configuration:

acl_check_data:

   deny    malware   = *
           message   = This message contains a virus ($malware_name).

If I'm receiving a virus the logfile contains:

2006-06-12 22:27:54 1Fpt0r-0004Dn-Ui H=(test.de) [192.168.33.72]
F=<marten@???> rejected after DATA: This message contains a virus
(W32.Badtrans@???).

Thats fine so far. But I don't want to block the mail right now, I just
want to notice that a virus has been found. And when I'm replacing
"deny" with "warn" I don't get any log entry about the virus. Where can
I find the warning?

Regards
Marten