EXCLUSIVE

Charlie Sheen is FURIOUS at Farrah Abraham for allegedly leaking their private text message conversation -- and TMZ has learned, he's already sent her the most epic rejection letter of all time ... calling her "a desperate guzzler of stagnant douche agua."

And that's just the beginning. Seriously. Charlie does NOT hold back. Here's the full transcript:

hey, you desperate guzzler of stagnant douche agua;

I truly do not recall giving you permission to globally reveal any communication between us. congrats on surviving your lobotomy and an even bigger congratz on the recent attempt at porn.

your daughter must be so proud.

please send my number to middle earth and if allowed, eagerly follow it into said abyss and slam the door behind you. the world will collectively sigh as the pungent memory of you vanishes into the pedestrian troposphere of lame-suck and zero-life.

oh and I'm sure they'll wave the cover charge when they see your tranny-boobs and five o'clock shadow.

bye!

cs.

TMZ broke the story ... Farrah reached out to Charlie back in May via text message, saying she hopes to meet Sheen if she can score herself a role on "Anger Management." Charlie responded favorably, agreeing to meet up, but now ... it appears that's changed.