Federal authorities began investigating the email acount of Michael D. Cohen, President Trump’s former lawyer, as early as July 2017, only months before Mr. Trump took office, according to documents unsealed on Tuesday.

The emails, dating from  January 2016, were sought by the office of Robert S. Mueller III, the special counsel conducting the Russia investigation, the documents show.

Hundreds of pages of documents well-nigh the inquiry into Mr. Cohen were released in response to a request by The New York Times and other news organizations.

Lanny J. Davis, a lawyer for Michael Cohen, said in a statement on Monday night that the release furthered Mr. Cohen’s “interest in standing to cooperate and providing information and the truth well-nigh Donald Trump and the Trump organization to law enforcement and Congress.”