For four years Clinton did all her State Department email through a personal account on a private server. In May 2016 the department’s inspector general found she had not sought approval, and that the officials responsible for security said they would not have approved it. She also did not hand over her work records when she left, as the rules required. She declined to be interviewed for that review. [1]
Comey said she used several different servers and administrators during her four years, and numerous mobile devices. FBI notes summarised by FactCheck.org show only 13 people emailed her address directly. [2][3]
Her reasons, she said, were convenience: one device. Critics believe the point was to keep her records out of reach of public-records requests. The record proves the effect — records were harder to get — but not the motive. [1]

Approved reader comments and ratings appear here when JavaScript is on.