[Mimedefang] Filtering received headers

[cc]

Hi,

I'm a bit lost as to where I should apply this issue or
even if it is a MIMEDefang option.

Seeing as spam can be visually detected via the Received:
headers, is it possible to get MIMEDefang to go through
the headers and check each received: address against some
DNSL site or even check the consistency of the received
headers?

Of course, this doesn't help with 'direct from source'
spam, but at least it can do forged ones.   I do recall
Spamassassin having that ability to detect forged headers;
so do I just run off a drop mail routine(or a redirect
to spamdrop mailbox) right after spamassassin tags it
as spam?

Any clarifications appreciated.

Thanks

Edmund