WASHINGTON — It was emailed to 388 administration officials every night as an attachment: a copy of President Trump’s private daily schedule, outlining his upcoming meetings and their locations, helping the White House staff plan around his day.

But since that schedule — which revealed that Mr. Trump’s day was often made up of large blocks of unstructured and unscheduled “executive time” — began regularly turning up in the hands of journalists, the White House has instituted a new system to crack down on unsanctioned “leaks.”

There are no more email attachments, according to two officials. Instead, the president’s daily private schedule is now shared on SharePoint, a Microsoft product that allows an administrator to monitor who has viewed the document. Based on how often people view the schedule, and when its contents become public, the White House has narrowed down its search for the schedule “leaker” to three potential culprits, a person familiar with the matter said.

Sarah Huckabee Sanders, the White House press secretary, said in an email that “we don’t comment on internal processes regarding the President’s schedule.”