The investigation into Clinton's use of a private email server was conducted by a number of FBI investigators, including Comey, who were using personal email addresses, the inspector general found.
Comey, Strzok and Page all at times used personal email addresses to conduct government business, according to the report.
"We identified numerous instances in which Comey used a personal email account (a Gmail account) to conduct FBI business," the report found.
The report noted that at a 2016 FBI conference in San Diego, Comey had said he had received "emails from some employees about this, who said, 'If I did what Hillary Clinton did I'd be in huge trouble.'"
"My response is you bet your ass you'd be in huge trouble," Comey said.