Joslyn James -- mistress #237 -- went to the LAPD Tuesday and filed a report, claiming Devon James -- mistress #424 -- threatened her life.

TMZ has obtained the email in question, which Devon sent to Joslyn's manager. As for the death threat, Devon wrote, "Trust me I will swear to u kill over this. Oh yeah and wait to u c wat ur prize has comming! Joslyn should b scared."

But here's the best part. Devon also writes -- referring to the Tiger porn spoof in which both woman starred -- "God if u saw her face when te cameraman said how f*ing hot I looked, and I quote 'Devons made the money shot.'"

And Devon's parting shot, "No wonder Tiger dummpppped her ass."