Internet entrepreneur Zander Wang has been forced to switch from the Gmail account he has used for years to Outlook. "It's a shame. Gmail is secure and has hardly any bugs. But I have to give it up," the 28-year-old said. "It has become the most difficult email to access in China, especially since my VPN services were blocked." Last month, the mainland clamped down on virtual private networks, the services that many rely on to breach the Great Firewall of online censorship. Wang said he bought a VPN for his iPhone at the Apple Store but it stopped working. He then bought a VPN application from Taobao, the mainland's largest online shopping platform. His new VPN used to be compatible with Google but last week it could only be used with a mainland-based search engine. "Apart from the money I've wasted, I've had so much trouble trying to reach people when I need them," Wang said. He's now completely cut off from Facebook and has lost contact with classmates from his days studying in the US. But Wu Ya, 27, who runs a tech magazine in Beijing, is having more success - he said he had figured out a way to fix his VPN. "It's like playing a game. When the Great Firewall is built higher, you need to make your ladder higher to get over it," he said. Wu said the game never stopped and the rules constantly changed. "We assumed the Great Firewall would never block Gmail and VPNs because foreign businesspeople needed the services. But now they're blocked," Wu said. "We fear that the worst might come when they block all international servers. In that case, it will force start-up entrepreneurs to leave China." " In the past year, online censorship has become tougher, with regulators shutting down more than 100 websites between April and November. Shenzhen-based entrepreneur Allen Wu, 34, built a VPN server in Hong Kong where his family lives, after his American VPN stopped working. "I got cold feet because of internet censorship. For two years I was so enthusiastic about investing in the Chinese IT industry. I thought then that the Great Firewall only blocked the general public, but allowed savvy internet users to access the internet freely," he said. "The worst thing is that the Great Firewall is blocking opportunities for Chinese to keep up with the most advanced technologies in the world. It's a losing game."