Patrick Gomes, 70, sent three letters to one of Lord Sugar’s business premises in Loughton between October and December 2018.
The businessman and star of The Apprentice said he had been reluctant to refer the matter to “already stretched” police but thanked officers in Essex for “helping to shine a light on the fact that this type of behaviour is simply not acceptable”.
The force said each letter was addressed directly to Lord Sugar and included abusive, threatening and offensive language. The letters were derogatory towards the Jewish faith.
Gomes was arrested at his home in Lyttelton Road, Leyton, on March 19 2019, after his DNA and fingerprints were found on one of the letters.
Officers found additional letters written by Gomes, all of which were discriminatory in nature. They also found the address the original letters were sent to listed in his address book.
Gomes denied involvement throughout the investigation but was found guilty at Chelmsford Crown Court on December 1 of religiously-aggravated harassment, putting those targeted in fear of violence.
Essex Police said he had failed to appear at court but a warrant was issued and he was arrested on December 2 and was remanded in custody to await sentencing.
A spokeswoman for Chelmsford Crown Court said a sentencing hearing has been listed for December 23.
Lord Sugar said: “I would like to pass on my sincere gratitude to the police for their assistance in this case.
“I have to be honest, I was reluctant to pass this matter on to the police as they are already stretched and have enough on their plates dealing with serious crimes.
“I would like to thank them sincerely for helping to shine a light on the fact that this type of behaviour is simply not acceptable and that racism or any form of discrimination is simply not acceptable.”
Investigating officer Pc Marc Arnold, of Epping Forest’s Community Policing Team, gesê: “Nobody should ever be subjected to this level of abuse or fear physical violence because of their faith.
“I’m really pleased that justice has been rightly served.
“There is simply no excuse for any hate crime and if this happens to you or you witness this type of behaviour, please tell us – we will not tolerate racism or discrimination of any kind and neither should you.”