"In a March 2015 interview, President Obama said that he had learned about Hillary Clinton’s use of a private email server as secretary of state “the same time everybody else learned it, through news reports.” But that assertion concerned aides of Mrs. Clinton, who knew that the president himself had received emails from the private address, according to a hacked email made public on Tuesday by WikiLeaks."
http://www.nytimes.com/2016/10/26/us/politics/wikileaks-hillary-clinton-emails.html
http://www.nytimes.com/2016/10/26/us/politics/wikileaks-hillary-clinton-emails.html