Through continuous innovation, NetEase's e-mail service users increased 18.2 percent to more than 650 million in the 12 months to March 2014. The majority of them use NetEase's free e-mail service and the company also offers charged e-mail services for its corporate and VIP users.

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Xiao Yuyan, product manager of NetEase's notary mail service, said that the service is at the beta testing stage and only open to users who have been invited to take part.

"The feedback is beyond our expectation," Xiao said, adding that users have put the service to creative use.

"One user who works in media and publication said she can use the notary mail service for intellectual property rights protection," Xiao said. "Once she finishes an article, she can send an e-mail to herself and, if necessary, she can get information from our server to know exactly when she sent the e-mail in order to prove she is the first one to have the content."

The notary service is free to paid users of NetEase's e-mail service. Users who want to add the function to their free e-mail service will need to pay about 30 yuan ($4.84) a month.

Mo said the charged e-mail is not a high-profit service but basically helps the company to "break even".

"We don't want to make huge money out of the e-mail service but through offering the service, we want more people to use NetEase's news portal and to play our games," he said. "Generally speaking, we use e-mail as a gateway to reach out more to Internet users."