A recently released email from Hillary Clinton when she was secretary of state appears to show her coaching an aide on how to send a fax on a non-secure system, renewing criticism about her perhaps skirting security measures.

Clinton wrote the email as part of an exchange in June 2011 that started when aide Jack Sullivan wrote to say his staff was having problems getting her documents on a secure fax.

Clinton responded by saying she hadn't received the documents and that Sullivan and his staff should “turn (the messages) into nonpaper w no identifying heading and send nonsecure."

Iowa GOP Sen. Chuck Grassley, chairman of the Senate Judiciary Committee, called the email, one of roughly 3,000 related to Clinton released Friday, “disturbing” and said it appears to show her “instructing a subordinate to remove the headings from a classified document and send it to her in an unsecure manner."

Clinton has been under criticism since news broke last spring that she had as secretary of state used a private server and email accounts for official business.

Grassley also said that the June 2011 email “raises a host of serious questions and underscores the importance of the various inquiries into the transmittal of classified information through her non-government email server."

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"How long has the State Department been aware of this email?” Grassley also asked. “Why is it just now being released? Was her instruction actually carried out? If so, has the FBI opened a criminal inquiry into these circumstances?"

Clinton has said she never knowingly sent or received classified information. However, the State Department, which under a Freedom of Information Act request is in the process of releasing roughly 55,000 pages of Clinton emails, is also retroactively classifying about 1,000 of her emails.

“This appears to be part of a pattern of behavior by Hillary Clinton where protocols designed to protect national security and our diplomatic efforts were cast aside,” Republican National Committee spokesman Michael Short said of the email. “Serious legal questions are raised by these emails.”