From CBS News:
President Obama said he heard about Hillary Clinton's private email server through news reports in March 2015 -- but an email from a Clinton aide around that suggests the president was emailing Clinton on her private address.
In the email, posted by WikiLeaks in the latest batch of emails hacked from Clinton campaign chairman John Podesta's account, Clinton communications staffer Josh Schwerin emailed a group of top aides noting that Mr. Obama
"said he found out HRC was using her personal email when he saw it in the news."
"We need to clean this up," Clinton aide Cheryl Mills replied. "He has emails from her - they do not say state.gov."
The exchange was in reference to an interview Mr. Obama did with CBS News’ Bill Plante, in which the president said he learned about the private email server "the same time everybody else learned it -- through news reports."