WASHINGTON — President Obama uses email as part of a specialized system allowing him to send and receive messages from only a limited number of high-ranking administration officials, the White House said Monday.

“There are some common-sense security measures that have put in place to protect the president’s e-mail. I think for obvious reasons, we don’t discuss a lot of those measures publicly,” White House Press Secretary Josh Earnest said. “But the fact that it’s not easy to predict exactly what the president’s e-mail address is, is in fact one of those measures.”

The White House has acknowledged Obama’s email use since the earliest days of his presidency, saying he uses it to keep in touch with a small circle of friends and senior officials. But the subject reemerged Monday following revelations that Obama used a pseudonym in his emails to former Secretary of State Hillary Clinton.

“Did you assume the president’s e-mail address was bobama@whitehouse.gov?” he joked to a reporter.

FBI records released last Friday disclosed for the first time that Obama e-mailed Clinton using an undisclosed fake name — a name so unremarkable that even Clinton’s closest aide had no idea who had sent it. (“How is this not classified?” Clinton aide Huma Abedin said when confronted with the Obama-to-Clinton email by FBI agents.)

Earnest said Obama uses email much as anyone else would: “He does a little business, but he also will exchange pleasantries and other personal notes via email as well,” he said. He declined to say how many cabinet secretaries and other administration officials enjoyed the privilege of emailing the president directly, but said the press secretary was among them.

How many e-mails does the president send? Earnest suggested it was a lot less than most people at the White House.

“But look, the president also has a system that most of us don’t benefit from, which is that he’s got essentially a staff secretary that can make sure that memos and things are delivered directly to him and then his response is appropriately circulated to people. So he doesn’t need to rely on it in the same way that presumably all the rest of us do in terms of handling basic, day-to- day functions,” Earnest said.