Help - How do I filter BCCs/Mailing Lists?

I hope someone can help me with this.

How do I set procmail to forward messages sent to a mailing list (i.e.
there is nothing in the To: field to indicate exactly who the email is
being sent to - it is hidden somewhere).  I am having the same trouble
with emails sent to a BCC: recipient.  Since the actual address is not in
the To: or CC: section, it slips by my recipes.

Can someone please email me if they have a suggestion/solution?

Thanks,

Eric