In a March 4, 2015 email to Hillary Clinton's lawyer Cheryl Mills, Clinton's eventual campaign chairman John Podesta asks if they should withhold email exchanges between Clinton and President Obama that were sent over Clinton's private server.

The day before Podesta sent his email to Mills, the House Benghazi Committeeprivately told Clinton to preserve and hand over all her emails. (The FBI report on Clinton's emails notes on Page 18 that on March 3, 2015, the United States House Select Committee on Benghazi provided a letter to the law firm Williams & Connolly requesting the preservation and production of all documents and media related to the email addresses hdr22@clintonemail.com and hrcl7@clintonemail.com.)

The email from Podesta to Mills, titled "Special Category," reads: "Think we should hold emails to and from potus? That's the heart of his exec privilege. We could get them to ask for that. They may not care, but I(t) seems like they will."

Mills did not respond by email. The Clinton-Obama emails were turned over to the State Department, which later announced it would not release them.

At the Jan. 29, 2016 State Department briefingspokesman John Kirby told reporters:

"As the White House has previously stated, Secretary Clinton and the President did on occasion exchange emails. As they have also said previously, such presidential records shall remain confidential to protect the President’s ability to receive unvarnished advice and counsel but will ultimately be released in accordance with the Presidential Records Act. I can confirm that 18 emails comprised of eight distinct email chains between former Secretary Clinton and President Obama are being withheld in full from the State Department’s FOIA production today of...former Secretary Clinton’s emails.

"The decision to withhold presidential correspondence from State’s Freedom of Information Act production of former Secretary Clinton’s emails was widely covered months ago. In response to a FOIA request, again, it is not unusual to deny or withhold a document in full. To be clear, the emails between then Secretary Clinton and President Obama have not been determined to be classified. They are entirely separate and distinct from the emails in today’s release that were upgraded to top secret, secret, or confidential, and I’m not going to speak again to the content of that email traffic."

The FBI report released this past July revealed that President Obama used a pseudonym in his email correspondence with Clinton:

(In her April 5, 2016 interview with the FBI, Clinton aide Huma Abedin was shown an email chain from June 28, 2012.  The FBI report said: "ABEDIN did not recognize the name of the sender. Once informed that the sender's name is believed to be a pseudonym used by the president, ABEDIN exclaimed: 'How is this not classified?'")

President Obama told CBS News on March 7, 2015 that he learned about Clinton's use of a private email server “the same time everybody else learned it, through news reports."

It was five days previously, on March 2, 2015, that The New York Times reported for the first time that Clinton had used a private email account and server to conduct official government business while serving as secretary of state.

On March 9, Obama's spokesman clarified that the president knew Hillary Clinton conducted business on a non-government email account while serving as secretary of state, but he had only recently learned the details of the privately run system, including her exclusive use of a private server. source