Under siege for her use of a private email account while secretary of State, Hillary Rodham Clinton is playing defense.

In an effort to quell concern among supporters about the questions surrounding the private email server, her campaign released a nearly 700-word memo Wednesday urging them to understand that "the truth matters."

The correspondence was sent a day after the Democratic presidential candidate announced she would turn over her private email server to the Justice Department. The move by her campaign to go directly to supporters comes as the publicly defiant candidate faced an onslaught of attacks on Wednesday by Republicans.

Clinton has received strong criticism in recent months for her exclusive use of private email while serving as President Obama's top diplomat. Questions have been raised as to whether her use of the server may have breached classified information.

In the memo, Jennifer Palmieri, Clinton's campaign communications director, contended that Clinton “didn't send any classified material over email.”

“No information in her emails was marked classified at the time she sent or received them,” wrote Palmieri. “She viewed classified materials in hard copy in her office or via other secure means while traveling, not on email.”

This spring, Clinton's personal office said that more than 62,000 messages were sent or received over her four-year tenure at the State Department. Half of those emails were listed as private by her office -- including messages about her daughter's wedding and her mother's death -- and destroyed.

The remaining emails were turned over to the State Department to be reviewed before they were made public. Last month, the inspector general for the intelligence community notified members of Congress and the Justice Department that some of the emails had information that should have been marked and handled as classified.

Clinton has remained steadfast in stressing that she wants all of her emails to become public.

“I want those emails out,” she has repeatedly told reporters.

Republican candidates including Donald Trump and Wisconsin Gov. Scott Walker issued statements attacking Clinton after her campaign said she'd turn over the server.

“She cannot be trusted to keep America's secrets or its citizens safe, and therefore cannot be trusted to be commander in chief," Walker said.