|You could contact the whoever runs the email server at the point of origin and ask them but I wouldn't hold my breath waiting for them to send you the personal information of whoever sent you the email.|
Typically though, this type of information requires a subpoena.
If this is a legal issue, contact the authorities.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.