[exim] Exim 4.69- defer message on malware scanner failure

Hello,
I'm currently trying to optimize my Exim configuration a little bit,
especially the malware ACL part. At the moment incoming messages,
which have marked as malware, are forwarded to a shared folder for
verification purposes. This process works very well.

Some days ago I realized that messages are not temporarily deferred
if the malware scanner ClamAV is not running but are forwarded to
the end user without being checked at all.

Now I wonder how I need to modify the ACL part to make sure that
this doesn't happen anymore. Is there any reliable way to find
out if the malware scanner is running or not?

This is the currently used ACL part:

acl_check_data:
  warn  log_message = This message contains malware ($malware_name)
        malware       = *

  warn  message       = X-Redirect-To: virus@???
        malware       = *
  ...

Thank you in advance for your help!

Regards
Juergen
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