BEIJING Internet users and company officials in China on Wednesday blamed a series of disruptions to cross-border email traffic on adjustments to the country's vast Internet surveillance system.
IT company executives offered varying explanations for the email disruptions, but agreed they were not a result of standard technical problems.
China is in the midst of a highly publicized campaign to rein in "unhealthy content" in its rapidly growing Internet, whose rapid spread of information regarding incidents of government corruption and rural unrest not reported in conventional media has alarmed China's stability-obsessed leaders.
"We have had hundreds of complaints from our clients in the last couple of days," said Richard Ford, technical director of Candis Group, a Beijing-based IT company that processes hundreds of thousands of emails a day.
"It would have been nice if the authorities could have warned us about this."
Ford said clients complained of emails being returned with error messages that could only have been placed by a "third party" between local and foreign mail servers.
"At first we thought this was our problem ... but after investigations, we are certain it is related to China's great firewall," Ford said, referring to the elaborate system of filters China maintains to intercept and block sensitive content from entering its sprawling Internet.
Several other IT companies managing email servers confirmed Internet users and clients in China and overseas had complained of having trouble sending and receiving emails.
"This often happens but usually only for a few hours, maybe a day at most," Gao Miao, IT manager at Beijing-based consultancy BDA China, told Reuters.
"But this has gone on for four days now ... Everyone knows that this is related to the government work on the great firewall," Gao said.
Several Chinese Internet service providers, including 263.com and Sina.com, have sent out warnings to email users about problems at the "international gateway" that could affect users' "overseas communications".
An executive at a Shanghai-based media company who asked not to be identified said his company had been advised by its email server managers to use local emails as a "new firewall system" was being installed at China Telecom and China Netcom, two of China's state-owned Internet service providers, and that this had led to "some overseas email being scanned and cleaned off".
The source said the new firewall system was to allow authorities to "temporarily" intensify their "monitoring and control" ahead of a key international meeting.
"He told me that it was related to a big meeting in August, the Shanghai Cooperation Organization ... After that, the controls would be lifted," the source said.
The Shanghai Cooperation Organization, which unites China, Russia and four Central Asian states against terrorism and cross-border crime, meets in early August in Urumqi, capital of China's northwestern Xinjiang region, before a major anti-terrorism exercise gets under way in Russia on August 9.
Officials contacted by telephone at China Telecom and China Netcom said they were unaware of email issues or of any work on China's international Internet gateway.
An official contacted at China's Internet industry regulator, the Ministry of Information and Industry, said he "had not heard" about work on the firewall.