China’s position is that the world’s second-largest economy is open to United States tech companies, but only on the ruling party’s terms. Those terms are essentially to do business through local partnerships, to host data on Chinese soil — where the government has access to it — and to remove anything the party deems offensive. Investing in these controls is the de facto tax on entering China.

Google has prominently refused those demands, which has for years made it a target of the Chinese government. Google does have limited business in the country, like ad sales, and it recently opened the Google Play store to Chinese developers, allowing them to build apps for Android devices outside of China. But the company’s consumer-facing services, like its search engine, have largely been disrupted or blocked since 2010. Chinese officials had insisted Google censor its search results, angering some top executives at Google, who refused to comply.

Some official publications have cited the company as one component of a Western conspiracy to undermine China, similar to accusations they make against Twitter and other American technology companies.

So while the latest Gmail-blocking tactics are new, the idea is the same: to block Google, wherever it is, in hopes of causing users enough frustration that they migrate to services like Baidu, a Chinese company that has a popular search engine here, that adhere to party rules.

People in China began noticing the new blocking of Gmail over the weekend, as their third-party mail applications failed to download emails from Gmail accounts if the users did not have V.P.N. software switched on.

For months, using such mail programs has been the most common way for people in China to keep using Gmail. The Chinese government blocked access to Gmail’s website and other Google websites around the 25th anniversary of the June 4, 1989, protests and fatal government response in Tiananmen Square.

But this new move frustrated Chinese and foreign Internet users in the country.

“It’s against the spirit of the Internet,” said Yuan Shengang, chief executive of NetentSec, a Beijing-based cybersecurity company, in a telephone interview.