Microsoft placed fifth in a new list of the world’s Top Ten spam hosts released this week by online security watcher Spamhaus.org.

The preamble to the survey results notes: “Spam continues to plague the Internet because a small number of large Internet Service Providers sell service knowingly to professional spammers for profit, or do nothing to prevent spammers operating from their networks. … The majority of the world’s service providers succeed in keeping spammers off their networks and work to maintain a positive anti-spam reputation but their work is undermined daily by the few networks who, out of corporate greed or mismanagement, choose to be part of the problem.”

Among the other notable members of the Spamhaus spam host shame list: wireless data service giant Verizon.com, weigning in at number nine…