The State Department has lost copies of a 2012 email between a former Hillary Clinton aide and a Clinton Foundation worker containing data about Greek bonds, which Chelsea Clinton's husband Marc Mezvinsky was heavily investing in during the Greek economic recovery.

The Washington Examiner says the fact Clinton's aide shared "insider information" about Greece's economic climate with the foundation a year, after Mezvinsky co-founded a hedge fund focusing on international economic trends, raises potential conflicts of interest.

"Why do the most important emails always end up missing? The State Department should explain to the American people why this information is unavailable, Citizens United's J.T. Mastranadi told the Examiner.

Mezvinsky founded Eaglevale Partners in 2011 and helped raise investments for a fund dedicated to "betting that the Greek bailout would raise the price of bonds," according to the Examiner.

Investors included Marc Lasry, CEO of Avenue Capital Group, who donated up to $250,000 to the Clinton Foundation.