Yahoo Emails review: email harassment 3

I'm requested to help Bidvest SA to trace a person sending harassing emails to the management, regarding sexual behavior of employees etc, which is untrue. Erica Gibbons (Erica.[protected]@bidvestbank.co.za) is the contact person at Bidvest Bank.
The email addresses are: [protected]@yahoo.com on 2017/02/28 at 20:35(GMT), adrian.[protected]@yahoo.com on 2017/02/20 at 09:30(GMT), [protected]@yahoo.com on 2017/04/12 at 07:43(GMT)
If you could please provide us with the logon IP addresses on that dates & times, so that we can subpoena the ISP's in SA.
A police criminal charge was laid. Ref Durban CAS 289/03/2017. An interim protection order was applied for, but because the person sending the emails is unknown; it cannot be issued.
We thank you for your assistance in this regard.

My contact details is
Lotie Brink
[protected]@digitaldetective.co.za
+[protected]