China has long had complicated relationship with Google, and for the past six months, several of the company's services have been experiencing disruption as a result of censorship believed to be related to the 25th anniversary of the Tiananmen Square massacre. As of last Friday, however, access to Gmail via IMAP, POP3 or SMTP has been completely cut off in the country.

Google's Transparency Report shows Gmail traffic falling dramatically on the night of December 25th. While a Chinese Foreign Ministry spokeswoman claimed to know nothing about the block, Google says it has checked extensively for problems and concluded there's nothing wrong at its end.

Dyn Research, an Internet analysis firm, did some checking of its own and found that the Hong Kong IP addresses through which Gmail access is routed, were being blocked. Members of, a China-based freedom of speech advocacy group, also commented on the blockade and noted that its impact might be felt beyond China's borders.

"I think the government is just trying to further eliminate Google's presence in China and even weaken its market overseas. [...] Imagine if Gmail users might not get through to Chinese clients. Many people outside China might be forced to switch away from Gmail."

China first blocked Gmail back in 2011 and the service has had to endure several outages in the country since then. Other sites that have been targeted in recent years include Facebook, YouTube, and Twitter, while government-sanctioned services are heavily monitored. Because of this, VPNs are often the only reliable access route to Gmail and other blocked services.