Hi Frits,
Thanks for your updates.
Currently, the information is not enough for us to clarify the root cause. Could you please provide the answers to the following questions to make the issue clearer?
1. When you mentioned “At a clients office the desktop app is working for some minutes and then it won´t work anymore”, do you mean Outlook 2010/2013 connected with the Office 365 account don’t work properly?
2. If so, where did you download Outlook 2010/2013? At the bottom of Outlook 2010/2013, there should be the connection status as the screenshot I posted in my last reply. Could you provide that here?
3. As for the OWA app for iPad, could you please connect your account to OWA app on other iPads to see if the issue exists? This can help us narrow down it’s caused by the app or the account.
4. When you mentioned “Just doesn't work, got no connection”, do Outlook just hang there and no responses when performing any actions?
Your efforts and patience are highly appreciated.
Regards,
David Zhang