This postmaster is a victim, but a victim due to ignorance or carelessness. Your report may help this person stop being victimized, hopefully before the site is black-holed . This victim is risking their entire operation, likely being victimized mainly by their software provider or their own incompetence. Reporting it to the appropriate legal authority in the location where laws have been violated, criminal charges may be filed, and you may even receive compensation for your loss, or a share in punative damages. Also, if the spammer is abusing a government domain, or fraudulently claiming to represent or derive authority from a government agency, that government entity may have strong powers to get it stopped.
Legal authorities take the position that they are the victim when the public is abused.
Some content commonly distributed in UBE, such as insider stock tips, may be illegal. Reporting such abuse to the appropriate governance may bring response that affects decision makers preventing that clientel of the spammer from ever hiring him, or ever again hiring him. Reporting it to the embassy of the country in which facilities are being abused to target you, may be appropriate in some circumstances. There are emerging nations, today, where Internet connectivity is an expensive emerging technology. Abuse of domains in these countries is an act of infowar against the country.