Sean Martin Duddy pleaded guilty to charges of threatening to kill and of attempted intimidation at the city's magistrates' court yesterday.
District Judge Barney McElholm was told one of the letters, threatening to have the victim shot, was posted to the victim's home address.
And a second letter, also threatening to have the victim shot, was posted to a priest in the Strathfoyle area of the city.
In the letters Sean Martin Duddy told the victim he had three days to leave his home "or you will be executed".
Both letters were signed "IRA, Creggan, Derry".
The 52-year-old's DNA was found on the letters following forensic examination.
A defence solicitor said Duddy, of Corrody Road in Gobnascale, had formed mistaken opinions about the victim and that he had since written a letter of apology to the man.
Mr McElholm said while it was a somewhat "amateurish offence", it was nevertheless a "wicked and malicious" attempt to intimidate someone to leave their home.
As well as imposing a six-month suspended jail sentence, the District Judge ordered Duddy to pay his victim £300 compensation and warned him that he had to pay the full amount within six months.