If while during the processing of Received headers a 10.0.0.0/8 address is detected, after a public IP address has been seen, then surely after that any IPv6 headers are moot? No need to extend the software to report such spam.
As already mentioned, all a spammer has to do to evade spamcop reporting is to add a header such as:
Received: from EXIGE.hsc.net.ou.edu ([10.101.1.10]) by
EX-HUB-02.hsc.net.ou.edu ([fe80::7818:b035:6799:d151%10]) with mapi; Thu, 19
May 2011 04:31:36 -0500
The Received header above that is:
Received: from EX-HUB-02.hsc.net.ou.edu (ex-hub-02.hsc.net.ou.edu [10.101.1.13])
by smtp4 (8.14.4/8.14.4) with ESMTP id p4J9VOlQ011352
(version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT);
Thu, 19 May 2011 04:31:24 -0500
Above that:
Received: from smtp4.ouhsc.edu (smtp4.ouhsc.edu [157.142.11.65]) ...<snip>