While Gmail has always been very tough to access in China, it seems that it has now become fully blocked since December 26, and possibly by the Chinese Government itself. Previously, people were able to download Gmail through third-parties due to internet restrictions in China but it has now become completely impossible on all Chinese public networks.
China already blocks an array of Google services including its main search site, Google Maps, Google Docs, and Google Drive. The country began making access to Gmail more difficult in the run up to the 25th anniversary of the 1989 June 4th Tiananmen Square protests, but determined users could still access their accounts from apps via IMAP, POP, and STMP protocols. Now, it seems, Chinese censors have closed this loophole, leaving virtual private networks (VPNs) as the last remaining access route to Gmail and other blocked services.