Clinton became Secretary of State on January 21, 2009, and she stepped down on February 1st, 2013. On March 15th of the same year, her private email account was exposed. A hacker called “Guccifer” accessed the account of a former aide of Bill Clinton, Sidney Blumenthal, and the exposure revealed that Clinton had communicated with Blumenthal with a private email account. Screengrabs were published, which showed they had discussed sensitive issues relating to foreign policy. After that, not much happened, and it wasn’t until 2014 that the issue started to get more attention. In December 2014, Clinton provided 50,000 pages of emails that had been printed out, which followed a request from the State Department. In March 2015, she told reporters that she only used a personal email because she did not want to carry two devices for work and personal email. She deleted over 30,000 personal emails, and gave over 30,000 more to the State Department that were work related. 

Source: Digital Forensics and the FBI: How Today’s Tech Will Help Solve Hillary’s Email Investigation, The Global Dispatch, June 6, 2016.