Hillary Clinton said she never told a staffer to send classified information over a non-secure fax, responding for the first time Sunday to the latest batch of emails dogging her presidential bid.

"That did not happen, and it never would have happened because that's just not the way I treat classified information," Clinton said on CBS's "Face the Nation."

A new batch of correspondence released Friday by the State Department includes a 2011 email in which Clinton, then secretary of state, asked an aide to send information by email after attempts to send the document through a secure fax line failed.

"If they can't," Clinton wrote to the aide, "turn into nonpaper w no identifying heading and send nonsecure."

The State Department has said it has no evidence the email Clinton requested was ever sent, nor do the emails prove the document in question was actually classified. But Clinton's critics have seized on the email to support their case that she was careless with classified information.

Clinton said Sunday that it is "common practice" to send non-classified information over email, and insisted she was requesting only information that was appropriate for sending in such a non-secure way. She said the staffer involved, Jake Sullivan, wouldn't have emailed classified material.

"The important point here is I had great confidence because I had worked with Jake Sullivan for years," she said. "He is the most meticulous, careful person you could possibly do business with, and he knew exactly what was and wasn't appropriate."

"It's another effort by people looking for something to throw against the wall to see what sticks," Clinton said.

Under an order by a federal judge, the State Department has been regularly releasing batches of around 55,000 emails sent by Clinton using a private server during her tenure as secretary of state under President Obama. The agency released the first set last May, and the final one is due at the end of January.

So far, the emails haven't proven that Clinton knowingly transmitted classified information using her private email--and Clinton maintains that she hasn't.

But the FBI is continuing to look into the matter, and Clinton has suffered political blowback as the emails have raised many complicated questions about when sensitive information was classified, what information should even have been classified to begin with and whether she mishandled any of it.

Government watchdog agencies told the FBI back in July that out of a sampling of 40 emails, they'd found four containing information deemed to be classified. The emails themselves weren't marked classified at the time, but the CIA has affirmed that two of them contained "top secret" material.