If this is the case, the message would still qualify as an internal one. However, it could still be intercepted since there is no way of filtering out the internal conversations from the external ones beforehand, Farr said. Such a selection would have to happen after the emails are intercepted.
Privacy International said the government is conducting mass surveillance by intercepting and scanning through communications in order to work out whether they are internal or external.
"Classifying communications as 'external' allows the Government to search through, read, listen to and look at each of them," the campaign group said. "They consider that such interception 'has less importance' than whether a person actually reads the communication, which is where the Government believes 'the substantive interference with privacy arises,'" the group said, adding that even when privacy violations happen, the government doesn't see it as an "active intrusion" because the analyst reading or listening to an individual's communication will inevitably forget about it anyway.
The group and its fellow plaintiffs called for an end to this "wholesale violation" of Britons' right to privacy.
Sign up for CIO Asia eNewsletters.