In the email obtained by TMZ, Packer wrote: "I'm in love with you and can't wait to get married and be together forever."
He then went on to say: "There's a song I'm listening to now that's got lots of meanings and I hope it makes you smile. When you get caught between the moon and New York City best that you can do is fall in love."
"All my love, laughter, light, respect and appreciation and admiration...Thank you my fiancee and soulmate."
TMZ also reports that a week before getting on a yacht with Packer on September 14, Carey gave him a Cartier wedding band as a birthday present.
The emails come after numerous rumours have emerged about why the A-list couple had a fight in Greece and suddenly ended their relationship.
Carey is reportedly blaming her breakup with Packer on Scientology influences, according to sources close to the superstar.
The New York Post reports those sources say she believes Packer's business manager Tommy Davis, a former Church of Scientology spokesman, poisoned their relationship.
Insiders in Carey's camp claim Davis took control of Packer's finances, and even allege he has put the billionaire on a detoxification program known at the church as a "Purification Rundown" and ordered Packer to "disconnect" from the diva.
Sources close to Packer strongly deny this and say his split with Carey was due to her excessive spending and the drama surrounding her as she films a reality show for E!
The couple are reportedly "deep in settlement negotiations" as they flesh out the details of their very public split.