@tlpeter I got 2 mails from Avaya:
Hi Erwin,
There is currently no support for mobile Windows platform.
Thanks,
Mark.
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Hi Erwin,
Thank you for your interest in the Avaya One-X Mobile Preferred application. We continue to actively develop the iOS and Android versions of the app but we currently have no plans to port it to the Windows mobile environment.
Regards,
Robert