Spanish newspaper AS claim to have seen the message which informed Costa that he would play no part at the Premier League champions next season.
According to AS, the full message read: “Hi Diego, I hope you are well. Thanks for the seasono [sic] we spent together. Good luck for the next year but you are not in my plan”.
Costa’s response was reportedly just “OK”.
Earlier this week, the 28-year-old striker revealed the existence of the message and claimed the club wished to sell him.
“I'm a Chelsea player, but they do not want me there,” Costa said while speaking to journalists after Spain’s 2-2 draw with Colombia on Wednesday.
“Antonio Conte has told me by message that I do not follow at Chelsea and that's it. Conte said he did not count on me for next season.”
Costa scored 20 goals in Chelsea’s title-winning campaign, leading the line in all but three of the club’s league fixtures.
Costa's future at Stamford Bridge came into doubt in January following a training ground row with a fitness coach, after which he was dropped by Conte for the 3-0 win at Leicester City.
The former Atletico Madrid frontman is known to be of interest to clubs in the Chinese Super League, his likeliest destination this summer.
Earlier this year, the owner of Tianjin Quanjian admitted to lining up a bid for Costa, only for it to be scuppered by the league’s rules on foreign players.
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