The discussion of troops to Bahrain reveals how routinely sensitive information is emailed on unclassified government servers, reflecting what many officials describe as diplomacy in the age of the Internet, especially in urgent, fast-developing situations. A review of the 30,322 emails from Mrs. Clinton’s private server that the State Department has made public under the Freedom of Information Act provides an extensive record of how such sensitive information often looped throughout President Obama’s foreign policy apparatus on unclassified systems, from embassies to the United Nations to the White House.