Originally Posted by PR_Tom

Of course. Find the spammers host, email them about the spam, and CC your complaint to the hosts upstream provider. This has to do with Spam. If it's not compliant, complain to the right people. It's effective to have a host's upstream provider telling them to put a stop to the domain sending spam. The host would rather keep their bandwidth I'd say than keep one client sending unsolicited emails.

Complaining about a sponsor being advertised in spam is just the wrong place to complain if you want the emails to stop coming.