A council worker sent a letter threatening a man that he would be "sorry" if he spoke to gardai in the course of a criminal investigation, a court heard.
Father-of-two Anthony Peppard (38) was traced through the post office stamp in what was described as an "amateurish" attempt at intimidating the victim and his family.
The note went on: "You have been warned."
Judge Hugh O'Donnell told Peppard he would not jail him if he paid €2,500 compensation.
Peppard, of Ventry Park, Cabra West, pleaded guilty to a charge of coercion in the incident in north Dublin. State Solicitor Aisling Kelly told Dublin District Court the DPP had directed summary disposal of the case.
The victim was involved in another investigation, the letter was sent to his family and he decided to report the matter to gardai.
Peppard had been fully co-operative with the gardai and there had been "no great reality" to the threats he made being carried out, his solicitor said.
The letter was "immediately traced" through the post office it was sent from.
"It was quite an amateurish attempt," the defendant's solicitor said. "He was apprehended quickly. He is very apologetic and very remorseful for what happened."
The court heard the defendant had worked for Dublin City Council for the last nine years and had no previous convictions of any kind.
Peppard had been "in the doghouse" since the offence came to light and it had had a heavy toll on him.
"He brought it on himself, it's all his own making," Judge O'Donnell said.
The defendant's solicitor said Peppard had not realised the gravity of what he was doing at the time and he had not tried to run away from it.
The court heard the victim was distressed and upset on getting the letter.
Judge O'Donnell adjourned the case to July 6 for payment of compensation.
"If that is paid, I won't impose a custodial sentence," the judge said.
Peppard was remanded on continuing bail.