The 53-year-old heartthrob wooed his British lawyer love through the rather formal mode of communication after Amal refused to take his phone number.
"I think the reported hottest man in the world should meet with the hottest human rights lawyer in the world", wrote Hollywood's most celebrated bachelor to Amal after the pair had been introduced by a mutual friend at a charity-fundraising event last September.
"It was all very tongue in cheek but it got the ball rolling," said a friend of the couple. "Amal found it funny, but she still made him wait a few days before replying."
"Once she replied that was it – it's been non-stop ever since."
The source added: "At first Amal was playing very hard to get and would not take his phone number, which simply made George even more intrigued.
"In the end he managed to get her email address and began sending her a series of flirty messages. He was very up front and joked about the fact they were both considered the hottest people in their respected professions."
George Clooney proposed to fiancée Amal Alamuddin in April
The hot couple have enjoyed a whirlwind romance ever since, including a series of dates around the world, a safari in Tanzania, a holiday in the Seychelles and a screening at the White House.
The human rights barrister and the Hollywood actor have also been on double dates with George's long-time friends Cindy Crawford and her husband Rande Gerber, as well as Emily Blunt and her husband John Krasinski.
Amal, 36, works at London's Doughty Street Chambers. She has represented Wikileaks founder Julian Assange in court and is an adviser to former UN secretary general Kofi Annan.
She was voted the hottest barrister in London last year by the blog Your Barrister Boyfriend, while George has often been voted the world's sexiest male.
Traditional romantic George is said to have gone down on bended knee on 22 April after cooking the tri-lingual beauty a meal.