Richard J. wrote:

In my experience, most of the delinquent posters who insist on
crossposting utl have verizon.net as their ISP, who appear to take no
notice of complaints about their users. If you've got the time
though, you could try bombarding them with complaints. Unfortunately
the originator of most of the crossposting keeps changing his apparent
address in order to defeat killfiles.

Although setting up a Delete rule on 'From' or 'Subject' manages to catch
most of the postings, since they are predominantly on the same subject and
he doesn't tend to change his name that much.