US vice president Mike Pence used a private email account to conduct public business when he was Indiana's governor, according to reports.
The Indianapolis Star said emails provided through a public records request show Mr Pence communicated with advisers through his personal AOL account on homeland security matters and security at the governor's residence during his four years in the post.
He also faced email security issues. His AOL account was subjected to a phishing scheme last spring, before he was chosen by Donald Trump to join the Republican presidential ticket.
Mr Pence's contacts were sent an email falsely claiming that the governor and his wife were stranded in the Philippines and needed money.
He moved to a different AOL account with additional security measures, his spokesman Marc Lotter said, but has stopped using the new account since he was sworn in as vice president.
Mr Lotter said Mr Pence "maintained a state email account and a personal email account" like previous governors in the state. At the end of his term, Mr Pence directed outside counsel to review all of his communications to ensure that state-related emails were transferred and properly archived by the state, the spokesman said.
As Mr Trump's running mate, he frequently criticised Hillary Clinton's use of a private email server as Barack Obama's secretary of state, accusing her of deliberately keeping her emails out of public reach and shielding herself from scrutiny.
Mr Lotter said "the comparison is absurd" because Mrs Clinton had set up a private server in her home at the start of her tenure at the State Department and, unlike Mrs Clinton, Mr Pence did not handle any classified material as Indiana's governor.
The newspaper reported that the office of Mr Pence's successor as Indiana governor, Eric Holcomb, released more than 30 pages from Mr Pence's AOL account, but declined to release an unspecified number of emails because they were considered confidential.
Public officials are not barred from using personal email accounts under Indiana law, but it is interpreted to mean that any official business conducted on private email must be retained to comply with public record laws.
The state requires all records pertaining to state business to be retained and available for public information requests. Emails involving state email accounts are captured on the state's servers, but any emails Mr Pence may have sent from his AOL account to another private email would need to be retained.
At the end of his term, Mr Pence hired Indianapolis law firm Barnes & Thornburg to review all his communications and that review is continuing, Mr Lotter said.
Any correspondence between the AOL account and any aides using a state email account would have been automatically archived, he added.