Something more we can all do: Sender Policy Framework.
http://www.openspf.org/index.html
also
http://www.ietf.org/rfc/rfc4408.txt
The gist of it is the SPF record in the DNS identifies all the valid hosts that are allowed to send mail for that domain. Mail should not be accepted for domains with an SPF record if the originating host is not in the SPF record.
Anything that reduces spam gets my vote!
You can check your domain for this and related details at
DNS Report.