Yahoo, as detailed in an explosive new report, does precisely that that. According to Reuters, in 2015, the company built, at the U.S. government’s request, software that scans literally all emails for certain information provided by either the National Security Agency or the FBI. It’s not clear how often it was used, or why this seems to have gone unnoticed in Yahoo’s biannual transparency report. In the latter half of 2015, the company received 4,460 total government data requests, for 9,373 accounts, that it would classify as “Government Data Requests,” a category that includes National Security Letters from the FBI and Foreign Intelligence Surveillance Act requests.

Source: Apple, Microsoft: We Have No Govt Email Scanning Program Like Yahoo’s – Vocativ

Apple, MS and Google are claiming they don’t have a similar program, but it could very well be a case of that they just don’t know they have such a program.