A Boston man has pleaded guilty to accusations that he hacked into the e-mail of a Middlesex probate judge and sent harassing messages and phone calls to his cellphone and relatives for three years. Jay Korff was ordered to serve two months of a 2-year prison sentence, with the remaining time suspended for 10 years. The 54-year-old Korff pleaded guilty yesterday to nine charges, including criminal harassment, threats, and unauthorized access of a computer. The Middlesex district attorney’s office did not name the judge harassed and threatened by Korff. Prosecutors say Korff caused the victim and his family anguish and anxiety and described the actions as deliberate and calculated attempts at targeting the very core of the judicial system.