Former Everton and Arsenal striker Francis Jeffers has admitted sending his wife menacing messages on WhatsApp that left her "fearing for her life".
The Crown Prosecution Service (CPS) said the 38-year-old, of Croxteth, sent the messages on 30 May after suspecting Lucy Jeffers was having an affair.
Liverpool Magistrates' Court was told he wrote that she would not need her clothes as she "would be in a coffin".
He was fined £625 and ordered not to contact Mrs Jeffers for 12 months.
The CPS said he sent the messages after his 20-year relationship with his wife broke down.
Mrs Jeffers, who had been married to him for 10 years but had told him the relationship was over, reported the correspondence to police and told officers it "left her genuinely fearing for her life".
CPS prosecutor Sophie Leyland said: "His motivation for sending the messages is irrelevant... he has caused his wife real distress.
"Emails and social media messages have real impact and it's important that people think long and hard before they send messages."
She said Mrs Jeffers had shown "courage to report what has happened to her".
"Hopefully publicity around cases like this will help others facing similar distress to come forward and [also stop] potential perpetrators from doing it in the first place."
Jeffers, who works as a youth coach for Everton, began his career with the Merseyside club, before moving on to Arsenal, Sheffield Wednesday, Motherwell and Australian side Newcastle Jets.
He made one appearance for England, scoring on his debut in a friendly against Australia.