[exim] Image spam stopping...

I've noticed and read up to confirm, most image spam comes in with the
following in the header. I have an ACL rule already in acl_smtp_mime as
follows:

deny    message = Image SPAM detected: message denied
      condition = ${if eq{$mime_content_type}{multipart/related}{1}{0}}

I'm looking for this:
Content-Type: multipart/related;
    type="multipart/alternative";

If I wanted to expand my rule above to also require matching of the
multipart/alternative, how would I do that since they're in the same string?

If anyone has other more effective ideas to stop image spam, I'm open to
suggestions. The rule above has caused some issues with false positives for
me.

Thanks,
James


James R. Price
Digital Chicago Networks, Inc.
3636 S. Iron St., Chicago, IL 60609
Tel/Fax/Cell: 800-603-0769
Web: www.digitalchicago.net
Email: james@???