But the courtside-seat email, sent to the mayor from one of the men, Jona S. Rechnitz, was not among them.

That correspondence, showing a particularly transactional relationship between Rechnitz and the mayor, as well as another previously undisclosed email, emerged this week during a police corruption trial in U.S. District Court in Manhattan.

Mayor Bill de Blasio and his staff are required to keep records that are connected to his government work. That includes emails about public activities that are sent to private email accounts. If someone requests the mayor to do something in his capacity as an elected official, those emails would be subject to public review.

Councilman Ritchie Torres said he would call on the newly appointed commissioner of the Investigation Department, Margaret Garnett, to look into the matter.

“It’s an occasion for the new leadership of DOI to demonstrate independence in the clearest possible terms,” Torres said in an interview. “It strikes at the core of DOI’s function, which is good government.”

Under the City Charter, both the mayor and the Council have the power to direct the Investigation Department to conduct an inquiry. “The Council takes its oversight role seriously and believes an investigation into the matter is warranted,” said Jennifer Fermino, a spokeswoman for the Council speaker, Corey Johnson.

Rechnitz, 36, a real estate investor who sought influence through political donations, has admitted bribing police officials, and said he also bribed the mayor, who received more than $150,000 in contributions for his political campaigns and causes from Rechnitz before and after becoming mayor.

The mayor has denied the bribery allegations, and has not been accused of wrongdoing. Nevertheless, the donations garnered access for Rechnitz, including to the personal inbox of de Blasio.

In one email that emerged Wednesday as Rechnitz testified in the police trial, the donor pleaded with the mayor to persuade Philip Banks III, a high-ranking Police Department official who had received gifts from Rechnitz, to rescind his planned resignation.

“What can we do for you to refuse Banks’ resignation?” Rechnitz wrote.

Months earlier, Rechnitz had invited the mayor to share courtside New York Knicks tickets with him.

“For the two percent chance your schedule permits and you’re in the mood, care to join me in my courtside seats tomorrow?” Rechnitz wrote to the mayor in a February 2014 email, with the subject, “Knicks tomorrow.”

The mayor, just over a month into his first term, responded within five minutes to Rechnitz. The mayor declined the invitation, but said he wanted “to profoundly thank you for all the help you’ve given lately. Means a lot to me.”

Eric F. Phillips, the mayor’s press secretary, said that the reason the correspondence unveiled at the trial was not given to reporters last year was that City Hall did not find the emails during their search.

Asked whether de Blasio deleted the emails, which were first reported by Politico, Phillips did not directly reply.

“The email isn’t in our possession,” he said. “And he wasn’t required to retain it.”

Another mayoral spokeswoman, Natalie Grybauskas, said in a written response Thursday that “City Hall only retains emails when they are certain types of public records, like audits, personnel actions, policy memos, final reports or emails that are subject to ongoing information requests or litigation.

“This is a Bloomberg-era email retention policy that has not changed. City Hall employees are under no requirement to retain every email ever written or received.”

The explanation suggested that untold other emails had not been kept — in other words, deleted — well beyond the two that came to light at the trial. City Hall maintains this is legal and appropriate.

John Kaehny, executive director of Reinvent Albany, a government watchdog group, disagreed, saying that the mayor’s nondisclosure of the emails was a clear violation of the public information law.

“There is no doubt the mayor should have disclosed these emails,” Kaehny said.

“The question is, was the mayor contacted as Bill de Blasio the person or Bill de Blasio the mayor? There is no doubt that he was contacted as the mayor,” Kaehny said, adding that the mayor should be sanctioned for his failure to do so.

The federal trial is the second in which Rechnitz provided key testimony and described his efforts to use political donations to de Blasio and other officials as a means of furthering his own ambitions. The first case involved the former head of the union for city correction officers, Norman Seabrook, who was found guilty in April of accepting a bribe in exchange for steering millions of dollars in union money into a risky hedge fund.

During that trial, another email from Rechnitz to de Blasio also surfaced that had not been turned over to reporters. At the time, Phillips told Politico that “there was no such email in the city’s possession.”

The current bribery trial is focused on the actions of two defendants: Jeremiah Reichberg, a friend of Rechnitz’s, and a former Police Department deputy inspector, James Grant. Prosecutors have accused Reichberg, who once hosted de Blasio at his Brooklyn home for a fundraiser, and Rechnitz of paying top officials and police leaders for special treatment. Grant is one of several officials accused of taking them up on their offer.

The overlapping federal investigations into the tangled web of political fundraising, bribery and corruption have cast a shadow over City Hall since their existence came to light in the spring of 2016.

Neither de Blasio nor any of his top aides were accused of a crime. In closing their investigations into his fundraising activities, the Manhattan district attorney and the U.S. attorney in Manhattan offered criticism of his actions in 2017, even as they stopped short of bringing charges.

The New York Times

J. David Goodman © 2018 The New York Times