Former Secretary of State Hillary Clinton told reporters earlier this year that she chose to use a personal email server for “convenience,” opting to carry just one device while she served at the State Department. But her use of a personal email server for official purposes has been anything but convenient for the agencies charged with reviewing her emails for public release. The choice has created major headaches for the agencies as they grapple with the issues raised by the situation: a cabinet-level official with access to wide sources of potentially classified information using her own email server to send...