Huang Chengqing, secretary general of the Internet Society of China, has disclosed that ISC has closed down the open email proxies and relays of more than 4300 email service providers.

Huang says as many email servers in China have a forwarding or open relay feature, they have been made used by illegal spam senders from foreign countries to send spam to users. Huang says the other problems of spam will be solved through two measures. One is to open a spam email reporting center and the other is to set up a white list mechanism to rank the credit status of email servers.

An open relay can be used to anonymize connections to open relays, further complicating tracking a spammer down. Open relays are a vestige of the early days of the Internet, when many mail servers were kept open to allow email to travel among different networks. Although they helped the Internet grow, they were abused by spammers, who have used them to disguise the origin of their messages.

International anti-spam organization Spamhaus has been working in China for a few years and frequently reports that open relays are a main reason many email providers end up in its XBL blacklist. The XBL targets spammers who use exploited systems to spam out of. These spammers criminally use open relays, open proxies, and PCs they have infected with viruses.