HOUSTON (Reuters) - U.S. Secretary of State Rex Tillerson, while chief executive of Exxon Mobil Corp XOM.N, used an alias for emails with employees and board members because his primary account was jammed with too many messages, the oil company said on Tuesday.

U.S. Secretary of State Rex Tillerson arrives in Mexico City, Mexico February 22, 2017. REUTERS/Carlos Jasso

New York Attorney General Eric Schneiderman, who is investigating whether Exxon misled shareholders and the public about climate change, wrote to a judge on Monday accusing Exxon of not previously disclosing the alias and Tillerson’s climate-change communications through it.

Exxon denied trying to hide anything.

“This was not an alias used to discuss only climate change,” Exxon spokesman Alan Jeffers said on Tuesday. “It was an account used for everyday business by senior executives who needed to reach” Tillerson, who left the company at the end of 2016 to become secretary of state.

Tillerson received thousands of emails a day from climate change activists and others at his regular address - Rex.W.Tillerson@ExxonMobil.com - and that made it difficult to parse which messages were important to promptly address Exxon’s business operations, Jeffers said.

Tillerson used the email alias for eight years and sent thousands of messages. Sixty-four of those sent and received met the parameters for Schneiderman’s climate change subpoena and were turned over to New York officials, Jeffers said.

The email alias was Wayne.Tracker@ExxonMobil.com. Wayne is Tillerson’s middle name and “Tracker” is likely a reference to his past involvement in the Boy Scouts of America.

Although Trump has vowed to reverse climate-change steps taken by former President Barack Obama, Exxon has said it believes it must address climate change. On Monday, it said: “ExxonMobil believes the risk of climate change is clear and warrants action.”

Darren Woods, who succeeded Tillerson as Exxon’s CEO in January, does not use an email alias, nor does any other Exxon employee, Jeffers said.

Use of the email alias was seized upon by environmentalists on Tuesday, who said it revealed a pattern of deception.

“If they had nothing to hide, than why the secret email account?” said Jamie Henn of 350.org, an environmental group.

Exxon plans to respond to Schneiderman in a court filing within the next several days, Jeffers said.

The case is People of the State of New York v PricewaterhouseCoopers and Exxon Mobil Corporation, New York State Supreme Court, New York County, No. 451962/2016.