Hillary Clinton’s emails were in the spotlight again on Thursday, as the State Department confirmed to the Associated Press that she had failed to turn over a 2010 email where she discussed her personal account with her aide, Huma Abedin. The omission raises questions about what other emails were potentially missed.

From the AP:

The email was included within messages exchanged Nov. 13, 2010, between Clinton and one of her closest aides, Deputy Chief of Staff Huma Abedin. At the time, emails sent from Clinton’s BlackBerry device and routed through her private clintonemail.com server in the basement of her New York home were being blocked by the State Department’s spam filter. A suggested remedy was for Clinton to obtain a state.gov email account. “Let’s get separate address or device but I don’t want any risk of the personal being accessible,” Clinton responded to Abedin. Clinton never used a government account that was set up for her, instead continuing to rely on her private server until leaving office.

The email in question was not part of the tens of thousands of emails that were turned over from her private server in response to public records lawsuits. “Abedin, who also used a private account on Clinton’s server, provided a copy from her own inbox after the State Department asked her to return any work-related emails,” the AP reports. “That copy of the email was publicly cited last month in a blistering audit by the State Department’s inspector general that concluded Clinton and her team ignored clear internal guidance that her email setup violated federal standards and could have left sensitive material vulnerable to hackers.”

“Secretary Clinton had some emails with Huma that Huma did not have, and Huma had some emails with Secretary Clinton that Secretary Clinton did not have,” Clinton campaign spokesman Brian Fallon said.