One is for all emails from Clinton’s personal account relating to Libya or the Benghazi terrorist attack. The committee had already received about 300 such emails from the State Department in February 2015. But on March 2, 2015, a New York Times article revealed that Clinton exclusively used a private email account hosted on her own private server, so the State Department may not have some of her emails.
Thus, the committee issues a subpoena directly to Clinton and her lawyers to see if more of her emails can be uncovered. The subpoena orders Clinton to produce emails from email@example.com. firstname.lastname@example.org, and any other email addresses she may have used while secretary of state, relating to the events surrounding the 2012 terrorist attack in Benghazi, Libya.
The other subpoena to Clinton is for documents it requested in November 2014 but still has not received from the State Department, relating to communications between Clinton and ten senior department officials. (House Benghazi Committee, 3/4/2015) (Federal Bureau of Investigation, 9/2/2016)
One day earlier, the committee asked Clinton for all of her emails. But this was only a request, not a subpoena.
Also on March 4, 2015, Clinton does not disclose the subpoenas, but tweets, “I want the public to see my email. I asked [the] State [Department] to release them. They said they will review them for release as soon as possible.” (The Washington Post, 3/10/2015) All of Clinton’s work emails will only be released after a judge orders the State Department to do so. (The Washington Post, 3/27/2016)