The email was made public by an angry Warner soon after he was banned from all football-related activity by FIFA's Ethics Committee on Sunday.
At the time the email was sent on May 18, Mohamed Bin Hammam of Qatar, the president of the Asian Football Confederation (AFC) was still standing against Sepp Blatter for president - but he was also banned by the ethics committee on Sunday on alleged bribery charges along with Warner.
Bin Hammam withdrew his candidacy to be president just hours before the ethics committee met on Sunday.
Warner showed the email from Valcke to Reuters, which stated: "For MBH (Bin Hammam), I never understood why he was running.
"If really he thought he had a chance or just being an extreme way to express how much he does not like anymore JSB (Blatter). Or he thought you can buy FIFA as they bought the WC (World Cup)'."
Valcke confirmed the authenticity of the email on Monday.
"It was a private email and we will discuss it. He sent me an email asking if I want that (Bin Hammam to run), he said that I should ask Bin Hammam to pull out."
Valcke said Warner had only published selected parts of the email, and he denied claims by Warner and Bin Hammam that he had influenced the ethics committee against them.
"The first time I met the chairman of the ethics committee was yesterday at 5 o'clock before we went to the press conference. I had no contact at all with anyone," said the Frenchman.
PLATINI FEAR
Meanwhile, UEFA president Michel Platini defended Blatter against other claims by Warner. One such accusation was that Blatter had offered to pay $1 million to the CONCACAF (the North, Central American and Caribbean) federation without finance committee's authorisation.
Warner said on Sunday that Platini was "annoyed" about this but the UEFA president told reporters on Monday: "It's not like that, it was a joke with me and Mr Blatter.
"He can give the projects that he wants to give. I joke, I said 'but Sepp this was not accepted by the committee' - but he can give many projects to many national associations.
"The president can give one or two projects to national associations - he has his own budget and he can give to one confederation and then it has to be approved of course by the executive committee next time."
Platini said he feared that there could be a repeat of the 1999 FIFA Congress in Los Angeles when Asian delegates walked out in protest over the number of World Cup places they had been allocated for the 2002 World Cup.
Platini said: "In '99 Asia left, I don't know if they will do that again. I think the (FIFA presidential) election (on June 1) will go ahead but I don't know."
Blatter told Reuters on Monday as he left the CONCACAF meeting that he was not worried about the threat of another Asian boycott.
"I have already faced that once and the Congress went on. They will be there I'm sure," he said
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