The company’s decision not to fight the order from intelligence officials caused Yahoo’s then-chief information security officer Alex Stamos to resign last year — and at least one other security staffer left the company — due to ethical concerns about the surveillance program, according to the person, who spoke on the condition of anonymity because the matter was confidential. Reuters, citing unnamed former employees, first reported the news Tuesday.

The government’s demand to scan email in real time alarmed privacy advocates, as did Yahoo’s compliance with such a broad order. Patrick Toomey, a staff attorney with the American Civil Liberties Union, called the order “unprecedented and unconstitutional.”

“It is deeply disappointing that Yahoo declined to challenge this sweeping surveillance order, because customers are counting on technology companies to stand up to novel spying demands in court,” he said in a statement.

Google, which runs Gmail, said in a statement: “We’ve never received such a request, but if we did, our response would be simple: ‘no way’.” Microsoft, another major email provider, said, “We have never engaged in the secret scanning of email traffic like what has been reported today about Yahoo.” Apple, in a statement said, “We have never received a request of this type. If we were to receive one, we would oppose it in court.”