I was recently contact by officials of an organization I belong too, apparently, someone sent an e-mail to a party that I know and have problems with saying some extremely nasty things, the header said it came from me, however the header was a complete fake. Three more e-mails copies went out anonymously with a copy of the one in question to high ranking officials of this organization, the e-mails came from "[email protected]" This was all done to make me look bad and have me thrown out of the organization. What can I do? I know who sent this, we both have Yahoo accounts. It's imperative to my good standing and reputation that I prove that A) I didn't send it and B) He did.
I'm not sure of the situation here. Was it sent using the organization's email, or sent via Yahoo? If it was via your organization, then the email system would have the IP that was logged in and sent it. Every corporate email provider that I know of can provide this, if it's not directly accessible. If it was via Yahoo or some other public service, then you need to speak with law enforcement. Yahoo won't release that information to the general public.
Of course, the IP may be available in the message header, if you can get hold of the header. For example, when I sent from my Yahoo account to my ISP account, the message header included:
"Received: from [xxx.xxx.xxx.xxx] by web36508.mail.mud.yahoo.com via HTTP; Sun, 05 Aug 2012 03:10:32 PDT"
The xxx.xxx.xxx.xxx masks my IP Address, the one I see when I go to the WIMI front page. If you can find the message header, and find a line like the one above, that may get you some of the evidence you need.
Maybe. If he went to an Internet cafe or some other public WiFi hotspot, you may not be able to prove that he did it. Only that you did not.