Russian Presidential aide Vladislav Surkov's personal chief of staff resigned, the Vedomosti newspaper reported on Friday.
Two sources close to the Presidential Administration told Vedomosti that Alexander Pavlov resigned in December over the leak of his boss' emails, which had been published online by Ukrainian hackers two months earlier.
Vedomosti was unable to reach Pavlov for comment.
Surkov's office told the newspaper that Pavlov resigned voluntarily, because he was "tired" after three years in the position.
The cache of emails from one of Surkov's work accounts was leaked by the Ukrainian hacker group known as Cyberjunta and contains messages dating from autumn of 2013 to the summer of 2014.
One message, dated May 13 2014, came from the assistant of Marshall Capital Partners owner Konstantin Malofeev, a Russian oligarch who has since been sanctioned in response to his involvement in Ukraine. The message offers a list of potential candidates for senior positions in the so-called Donetsk and Lugansk People's Republics in Ukraine. One candidate on the list, Alexander Zakharchenko, was appointed as head of the Donetsk People's Republic four months later.
The Kremlin has denied the authenticity of the leak. Presidential Spokesman Dmitry Peskov claimed that Surkov does not use email and suggested that the hack might be the work of U.S. intelligence agencies. Others have pointed out that the correspondence was handled not by Surkov personally, but by two of his assistants.