A second secret email address used by Hillary Rodham Clinton while she was secretary of state was revealed Monday.

The email address, published by The New York Times, was used in exchanges between Clinton and longtime adviser Sydney Blumenthal, and is from the same private email server that was uncovered earlier this year.

“Fyi. The idea of using private security experts to arm the opposition should be considered,” Clinton wrote Blumenthal from the ­email address HRod17@clintonemail.com.

The two were discussing strategies to help the opposition rebels oust Moammar Khadafy in Libya as that country descended into chaos in 2011.

Clinton’s office insisted just two months ago that the only private email address used by the former secretary of state during her tenure was hdr22@clintonemail.com.

In a 2015 letter to Rep. Trey Gowdy (R-SC), Clinton’s lawyer acknowledged that the HRod17 email address existed, but stated explicitly that it was “not an address that existed during Secretary Clinton’s tenure as secretary of state.”

The time stamps and content of the messages make clear that this statement was inaccurate, according to the Times report.

The first private email use was seen as a breach of protocol. Clinton’s advisers handed over 55,000 pages of emails to the State Department so they could comply with an investigation. But, according to Vice News, those emails will not be made public until 2016.

Clinton admitted to deleting thousands of others, claiming they were personal.

The revelation of a second email address raises questions about Clinton’s transparency and her relationship with Blumenthal.

The longtime Clinton confidant was not working at the State Department at the time, but advising American contractors that sought to do business in war-torn Libya.

In another email after Blumenthal suggested the new Libyan leader, Mohamed Magariaf, would “seek a discrete relationship with Israel,” Clinton wrote to her deputy Jake Sullivan, “If true, this is encouraging. Should consider passing to Israelis,” according to the Times.

Blumenthal’s coordination with Clinton raises the likelihood of additional scrutiny as she runs for the White House.

While he was not given a job in the State Department by the Obama administration, Blumenthal was employed by Bill and Hillary Clinton’s philanthropic organization, the Clinton Foundation, to help with research and “message guidance,” according to the Times.

At the same time, the Times reported, Blumenthal also was helping to craft Hillary’s 2016 presidential campaign message by working as a consultant to Media Matters and American Bridge.