AT&T worked for decades in a close "partnership" with the National Security Agency to retrieve information about billions of emails.

That's according to a report by the New York Times and ProPublica citing NSA documents obtained from former agency contractor Edward Snowden.

AT&T (T) gave the agency access to information regarding emails sent on its networks and allowed the agency to monitor communications at the United Nations, according to the documents. The article says AT&T provided the information under "legal rules."

It had already been known -- in large part because of documents leaked by Snowden two years ago -- that telecom and other tech companies were enlisted by the NSA in efforts to collect information from emails.

The article states that the documents show that AT&T's role with the NSA was far more extensive and intimate than other companies.

AT&T, in response to CNNMoney's request for comment, said Sunday that it only provides information to investigative agencies through a court order or "other mandatory process," unless a person's life is in danger and "time is of the essence."

The article, based on documents spanning from 2003 to 2013, details how AT&T helped the NSA before Snowden's massive leak of classified documents set off a global debate about how much personal information governments should be able to collect.

The documents, according to the article, don't actually name AT&T but use code names that the Times and Pro Publica concluded referred to the company.

The article states that it's unclear if AT&T has the same kind of relationship with the NSA today.

The NSA's dealings with AT&T reportedly was the agency's most expensive, costing more than double the second-most-expensive project in 2013.

According to the article, one document tells NSA officials to treat AT&T with special care. "This is a partnership, not a contractual relationship," one document reads.