Hillary Clinton has said that she should have used a government email account as US secretary of state, though she said she violated no rules.
She made her first public remarks over the controversy in a press conference at the United Nations in New York City.
Ms Clinton came under fire for using a private email account for official business when she was the top US diplomat because of concerns that she hid important facts about her tenure and put her correspondence at a security risk.
"I opted for convenience to use my personal email account, which was allowed by the State Department, because I thought it would be easier to carry just one device for my work and for my personal emails instead of two," she said.
"Looking back, it would've been better if I'd simply used a second email account and carried a second phone."
Ms Clinton, the presumed front runner for the 2016 Democratic presidential nomination, said she had provided all of her emails that could possibly be work-related for archiving purposes to the State Department .
She said she chose not to keep personal emails on topics such as yoga routines, her deceased mother's funeral arrangements or her daughter's wedding plans.
The former US senator and first lady insisted she had done nothing wrong and had complied with all government regulations.
She said that most of her official emails were sent to government addresses, which were automatically preserved.
She added that no classified material was sent via email.
Ms Clinton said her family's server would remain private and rejected calls that it be studied by an independent arbiter.
The State Department said that it would post Ms Clinton's emails on a website after a review that was likely to take several months.
Ms Clinton tried to head off criticism last week by urging the department to quickly review and release her emails.
Republicans, who have questioned her ethics and transparency, were not convinced.
"Regrettably we are left with more questions than answers," said Representative Trey Gowdy, a Republican who chairs a congressional committee looking into the Benghazi, Libya, attacks of 2012 that led to the deaths of four Americans while Ms Clinton was secretary of state.
"The Select Committee is left with no choice but to call her to appear at least twice," Mr Gowdy added in a statement.
Ari Fleischer, a former spokesman for Republican President George W. Bush, rejected Ms Clinton's explanation.
He tweeted "Personal convenience? Hah. She did it because she only trusts a few top aides and wanted total control".
Hillary was thoroughly unconvincing. Personal convenience? Hah. She did it because she only trusts a few top aides and wanted total control.
— Ari Fleischer (@AriFleischer) March 10, 2015Democrats were pleased that she addressed the issue but critical of the time it took to do so.
"By waiting so long to finally show her face and address it, I think it just allowed this thing to spiral out of control," said a former Clinton adviser, who spoke on condition of anonymity.
The adviser said: "There is an arrogance that comes with this operation to some extent that says that they don't have to play by the same rules. You know what? You do."
The issue has complicated what has been seen as a clear pathway to the Democratic nomination for Ms Clinton, who lost the 2008 primary race to Barack Obama.
But the issue may not resonate with voters or with the donors who will be critical to funding Clinton's campaign.
