THE BURNED OVER DISTRICT

And while they were kissing each other, they were giving the rest of us a jolly good rogering. And to show its love for NSA, AT&T freely gave NSA just about every e-mail that passed through its system, including those from the UN.

The National Security Agency’s ability to spy on vast quantities of Internet traffic passing through the United States has relied on its extraordinary, decades-long partnership with a single company: the telecom giant AT&T.

While it has been long known that American telecommunications companies worked closely with the spy agency, newly disclosed N.S.A. documents show that the relationship with AT&T has been considered unique and especially productive. One document described it as “highly collaborative,” while another lauded the company’s “extreme willingness to help.”

AT&T’s cooperation has involved a broad range of classified activities, according to the documents, which date from 2003 to 2013. AT&T has given the N.S.A. access, through several methods covered under different legal rules, to billions of emails as they have flowed across its domestic networks. It provided technical assistance in carrying out a secret court order permitting the wiretapping of all Internet communications at the United Nations headquarters, a customer of AT&T.

The N.S.A.’s top-secret budget in 2013 for the AT&T partnership was more than twice that of the next-largest such program, according to the documents. The company installed surveillance equipment in at least 17 of its Internet hubs on American soil, far more than its similarly sized competitor, Verizon. And its engineers were the first to try out new surveillance technologies invented by the eavesdropping agency.

One document reminds N.S.A. officials to be polite when visiting AT&T facilities, noting, “This is a partnership, not a contractual relationship.”

And a fecund partnership it was is. The other telecom's were also providing to the NSA, but there is little doubt that AT&T was the Number 1 concubine.