Blocking peek-through spammers

Due to an earlier stupidity of not disabling EXPN on my Sendmail, I now
have a bunch of spammers who are sending to me with the envelope mail_to
header of dvk@lonewolf.com, but the body To: header of designcenter@ibp.com
(which is what was on the web page last year).

I can block this with procmail, but I'd like to report it as spam on DCC
and prevent other people from getting it (and yeah, I know I can do that
through procmail too, via "dccproc -E -t many -c all,many"), but I'd like to
just have dccm/dccd filter it.  So I added this to my whiteclnt:

many	substitute to designcenter@ibp.com

But this doesn't work, because the mail header actually says:

To: designcenter@ibp.com (Murray Deininger)

Can I use DCC, or am I going to need to use procmail?

-Dan