The administration also issued a semi-apology for failing to inform the 16 deans of the fall 2012 search until after The Boston Globe reported about it Saturday night.
The email search was conducted after a confidential email sent to the resident deans ended up leaked to The Harvard Crimson student newspaper, the statement by Harvard Faculty of Arts and Sciences Dean Michael Smith and Harvard College Dean Evelynn Hammonds said.
That email, sent to the resident deans, who live in houses with students, was about advising students implicated in the cheating scandal investigation. One of the deans forwarded the email to a student he was advising, the Crimson said.
An initial inquiry into the leaked email's origin was not fruitful, the administration began "a very narrow, careful, and precise subject-line search" of the 16 deans' email accounts to identify the source of the leak, the statement said.
"The disclosure of a confidential board conversation led to concerns that other information -- especially student information that we have a duty to protect as private -- was at risk," the statement said.
"To be clear: No one's emails were opened and the contents of no one's emails were searched by human or machine," the statement said.
Harvard said it eventually determined the leaked information was an "inadvertent error" that stemmed from forwarded email that made its way to the newspaper. It said no action was taken against the dean whose email account was involved.
But after reaching that conclusion Harvard wanted to protect the dean who leaked the information, the statement said, so that's why it hadn't disclosed the searches to the full group of deans.
"We understand that others may see the situation differently, and we apologize if any resident deans feel our communication at the conclusion of the investigation was insufficient," the statement said.
The secret search was connected to a cheating scandal last May, when dozens of students cheated on a take-home final exam in a government class. About 70 students were forced to leave the Ivy League university.