While Clinton was secretary of state, she exchanged 18 emails with President Obama from her private email account. All information about these emails has remained classified. But some details are finally released due to a Freedom of Information Act (FOIA) lawsuit by Vice News.
All of the emails were exchanged between May 18, 2012 and January 31, 2013. Obama sent eight emails to Clinton, and the other ten were from Clinton to Obama. None of the emails appear to contain highly sensitive or classified information, but instead are thank you notes, holiday greetings, and the like.
All of the emails were withheld under presidential privilege and privacy act and deliberative process exemptions to the FOIA. The new details are formally submitted in what is called a Vaughn Index, a document prepared for FOIA lawsuits in which government departments justify the withholding of information. (Vice News, 09/15/16) (Vicc News, 09/15/16)
In February 2016, it was reported there were 19 emails between Clinton and Obama, not 18. It is unclear if the Vaughn Index is missing one or if the report of 19 emails was off by one.