Don't use the CL forwarding system. Check the "Don't display contact info" option, and then a the bottom of the post put this:
Thanks to CL's refusal to do anything about the spam responses, please e-mail me direct at -myemailaddress at mydomain dot com-
I've been having to do that for a while, every now and then i post in a hurry and forget to undo the anonymous reply, and get tons of spam.
If you want to keep their forwarding, then forward all your spam e-mails to:
[email protected], [email protected], and spam, abuse, report_spam or whatever other address their e-mail provider requests.