I found out today my former employer is sending out emails signed with my name denying actions that he committed that caused me to resign.
In other words he is trying to tell his clients that he didn't do anything wrong but is signing my name so it doesn't look like he is doing it and that it looks like I am still working there. Is there a legal action that can be taken to stop him from sending out these emails with my name?

You need copies of those emails, as many as possible. Bring them to a lawyer and have the lawyer write a cease and desist letter for you.

I would send a cease and desist regardless of whether you have copies or not.

May I ask you youy know he is doing this?

I was told by an employee that is still working there that he sent out emails in my name and her name. He has also done this to other past employees from what I was told. Anytime an employee quits he sends out emails in their name.