help with yahoo email: finding sender

Hi All:= I really think your guys for helping me out here with finding a sender of the email (yahoo email). I’ve recently recievd an email from an unkown person. He said something really bad in the email that’s been bothering me a lot. i do have suspect but I can tell for sure. I should be able to access the suspect’s computer even if it helps….Please help me out here. I know it’s from diffrent country that’s for sure. Please let me know what are the hopes?????????????????