You would need to contact your attorney in Michigan for a complete understanding of the laws in your state. Whether or not you can admit this email in court depends upon a number of factors. You will need to verify its authenticity and that it was in fact your ex writing or responding to the email. Generally speaking, e-mails are considered what is known as "heresay" and are inadmissible unless they fall under an exception to the heresay rule.  Get help.  Good luck.