The British intelligence organization GCHQ instigated a test exercise in 2008 that captured the emails of journalists and editors from Reuters, the New York Times, The Guardian, the BBC, NBC, the Washington Post and others, according to recently released files from Edward Snowden.
As a result of the test, the content of the emails was shared on the organization's internal servers where anyone in the organization could read them. GCHQ was tapping fiber-optic cables in November of 2008 when they intercepted over 70,000 emails, including emails from the mentioned news companies, according to The Guardian.
The motive of the test is unknown, but other Snowden documents have shown the NSA and other intelligence agencies regularly target investigative journalists, often putting them on the same target lists as terrorists.
British Prime Minister David Cameron recently called for the banning of encrypted messages that can't be intercepted by intelligence agencies. Applications like Facetime, iMesage and Snapchat send messages that are incredibly difficult for organizations to intercept.