How do I trace a particular yahoo email address. It is sending nasty information about a particular person.?

you need to go in to your email Options section look for something along the line of - long headers / short headers you want to put a check mark next to - long headers this opens up the vital information from the sender once you have this set up - open that email and send it to yahoo abuse check the yahoo site listed below for the proper yahoo abuse email address to send it to http://help.yahoo.com/help/us/mail/spam/

you could SPAM it

There is only one way to approach this if you are serious! See a lawyer, the lawyer will know how to approach yahoo to find out who the person is.

you can try and look in the member directory. usually the first part of the email address before the @ symbol is their user id. go to http://au.members.yahoo.com/ and type in the first part of the email address. It may or may not give you some info.