JeffM wrote:

snip

Instead of bothering with the anti-spam idiots at Google,
look at the headers. Do a reverse DNS on the Posting Host
and report the jerks to their providers (ISP or NNTP provider).

snip

Often the IP address does not resolve; instead do:
whois -h whois.arin.net ip addr
-- which may point to apnic.net or other authority
so you may need to repeat the lookup accordingly.

Then you will need to report to the owner of the IP block.

Michael