The plea was made in a court filing yesterday on behalf of James Everett Dutschke of Tupelo.
Dutschke is charged with sending the poison-tainted letters on April 8 to Obama, US Sen. Roger Wicker and Lee County Justice Court Judge Sadie Holland.
Dutschke had been scheduled for arraignment tomorrow in US District Court in Oxford.
His lawyer, George Lucas, waived Dutschke's right to appear and entered not guilty pleas to all five charges.
Lucas had no comment when contacted today.