Old email habits die hard — or at least that’s proved to be the case for a second Obama administration official.

Defense Secretary Ashton Carter used his personal email to conduct government business for nearly a year, according to emails released late Friday by the Department of Defense in response to Freedom of Information Act requests from the Associated Press and other news organizations. Carter used his personal email from taking office in February of 2015 through December.

While none of the emails sent to or from Carter’s personal account contained classified information — most were relatively mundane scheduling notes sent to his staff — his actions violated long-standing Pentagon policy. The New York Times first revealed Carter’s use of his personal email Dec. 17, upon which he and his staff admitted their mistake, saying they were not aware it was against the rules, and would stop immediately.

The use of a private email server by Democratic front-runner and former Secretary of State Hillary Clinton has been a material issue in the 2016 presidential campaign. Clinton’s challenger in the Democratic primary, Vermont Sen. Bernie Sanders, has downplayed the issue, but it’s almost certain to resurface in a general election campaign if Clinton becomes the nominee. Several Republican candidates have suggested Clinton should be indicted for her use of a private server. Clinton’s actions did not violate any laws but could be perceived as a way for her avoid having some emails automatically preserved by the federal record-keeping system, as would be the case for any message sent to or from a federal government email address.

According to the emails released in the Friday night news dump, as late as Nov. 18, Carter sent an email from his personal account saying that his work email was not working on his iPhone and advising the recipients to email him at his personal account and copy his government email.

On Dec. 18 — one day after the Times story — an auto-response from Carter’s personal email said that he would no longer be using his personal email while serving as defense secretary, and advised people to contact him on his cell phone for personal matters and his assistant for government business.

A Defense Department spokesman said in a statement to the AP that the email release proves that no classified information was sent from that account and that all of Carter’s government emails will be preserved as part of the federal records protocol.