During the 2016 presidential race, Mr. Trump repeatedly harped on Hillary Clinton’s use of a private account as secretary of state, making it a centerpiece of his campaign and using it to paint her as untrustworthy. “We must not let her take her criminal scheme into the Oval Office,” Mr. Trump said last year. His campaign rallies often boiled over with chants of “Lock her up!”
The F.B.I. closed its investigation into Mrs. Clinton’s handling of classified information and recommended no charges. But even after becoming president, Mr. Trump has prodded the Justice Department to reinvestigate.
While the private email accounts spurred accusations of hypocrisy from Democrats, there are differences. Mrs. Clinton stored classified information on a private server, and she exclusively used a private account for her government work, sending or receiving tens of thousands of emails. The content and frequency of the Trump advisers’ emails remain unknown, but Trump administration officials described the use of personal accounts as sporadic. The emails have not been made public.
“All White House personnel have been instructed to use official email to conduct all government related work,” Sarah Huckabee Sanders, the White House press secretary, said Monday in response to questions about the emails. “They are further instructed that if they receive work-related communication on personal accounts, they should be forwarded to official email accounts.”
The acknowledgment of private email use came as the White House is responding to a wide-ranging Justice Department request for documents and emails as part of the special counsel investigation into Russian election meddling. The use of private emails has the potential to complicate that effort, but the White House said it was confident in its process.
“I am dealing with honorable professionals and getting what I need,” said Ty Cobb, the White House lawyer leading the response to the investigation. “I am doing all I can to ensure the special counsel receives the materials they request.”
It is not clear why even sporadic use continued after a campaign in which email habits became a source of controversy. A former administration official noted, though, that in many cases, people received emails to their personal accounts. In some instances, officials used their private accounts to talk with reporters.
Most of Mr. Trump’s aides used popular commercial email services like Gmail. Mr. Kushner created a domain, IJKFamily.com, in December to host his family’s personal email. That domain was hosted by GoDaddy on a server in Arizona, records show.
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Mr. Priebus and Mr. Bannon did not respond to messages seeking comment. A person close to Mr. Bannon insisted he almost never used his private email for work purposes. A White House spokesman did not immediately respond to a question for comment about the current officials.
James Norton, a former senior homeland security official during the George W. Bush administration, said private accounts pose security risks — a criticism often raised against Mrs. Clinton.
“These private email accounts become targets of phishing attacks or other types of ways of collecting information,” he said. “It’s an issue not only for the person who owns that account, but the person who is receiving the emails. It is introducing risk into the system.”
Richard W. Painter, a chief White House ethics lawyer under Mr. Bush who is now the vice chairman of Citizens for Responsibility and Ethics in Washington, a watchdog group, said that there is often a “gray area” over what is considered official business. But, he said, “If it has anything to do with the president’s policy, including defending the president’s policy to the press, it’s very difficult to escape that being official.”
“I think Kushner was sloppy to do this,” he said. “I think Hillary was sloppy. I don’t think any of it was criminal.”
The special counsel, Robert S. Mueller III, is leading the investigation into Russian interference in the presidential election and whether anyone around Mr. Trump was involved. Mr. Mueller’s team has the power to subpoena a company to turn over customer emails.
White House officials hope it does not come to that. They have been hurrying to provide Mr. Mueller with the documents he has asked for. Mr. Cobb has described it as “full cooperation mode.” He has reminded White House aides to search their private accounts for records to give to Mr. Mueller.
The White House views such cooperation as its best chance to escape the glare of a special counsel investigation that also touches on Mr. Trump’s actions as president.
The private email accounts immediately triggered questions in Congress. Representative Trey Gowdy, Republican of South Carolina, who was among those who most vociferously criticized Mrs. Clinton’s email use, sent a letter to the White House and federal agencies asking about the Trump administration’s personal email use.
Representative Elijah E. Cummings, the senior Democrat on the House Oversight and Government Reform Committee, asked the White House to make sure that none of Mr. Kushner’s emails are deleted.
“Before requesting copies or calling for the public release of all official emails you sent or received on your personal email account,” Mr. Cummings wrote, “I first request that you preserve all official records and copies of records in your custody or control and that you provide the information requested below.”
“Your actions in response to the preservation request and the information you provide in response to this letter will help determine the next steps in this investigation,” he added.
Mr. Cummings noted that Trump administration officials had previously said that senior White House officials did not use multiple email accounts. And he reminded the White House about the grilling that Mrs. Clinton received from congressional Republicans over her email practices.
Both political parties have fought for years over the use of private email accounts. Long before Mrs. Clinton’s emails were a campaign issue, Democrats criticized members of the George W. Bush administration for the practice.