But the company was silent on the number of add-ons that had been found to be violating its Gmail policies. It said that third-party developers could collect and use Gmail users' data "long as they are transparent” about what they do.
Reuters reported that the search company has said in a letter that it used automated scans and feedback from security professionals to track what third parties, who had access to Gmail data did.
It cited the example of a company known as Return Path which used computers to scan about 100 million emails a day from Gmail, Microsoft or Yahoo! email inboxes of those who had signed up for a free app through its partner network. This company collects data for marketers through this scanning.
The report said, at one point, Return Path workers read about 8000 unredacted emails to train their company's scanning software.
A number of American politicians wrote to Google about the handling of users' personal information in the wake of this report.
The US Senate's Commerce Committee has set a hearing for 26 September to question Google, Apple, AT&T and Twitter about the way consumers are provided data privacy.
iTWire contacted Google and asked for a copy of this letter. In response, a company spokesperson said: "We addressed this topic in a blog post in July. Please refer there for details. We are checking with our policy team on the letter request."