Hi Rolf,
Basd on your two mail headers, I have found that two mail headers have the different “To” addresses.
One is xxx.se, the other is xxx.com. And these two emails are also created in different time.
Have you set auto-forwarding or proxyaddresses to this account?
Please help us to troubleshoot the issue, could you please close all the client (Outlook, phone, Ipad) and see if the emails always double in OWA.
Thanks,
Jason Jiang