how to get help with defamation of character?

a mass email was sent out to every one in my company that i was terminated, from the company , and this was not true .. this has my business in a mess. this came from a so called leader in the company not from any one in the corporate office.and i talked with the owner he knew nothing of this and i have gotten 1000 of inboxes , over 50 calls how this has went out .. i need help