After entering all relevant data, it is not possible to login on the OutlookAddIn.
An exact cause is still unknown.
Start an registry editor (for example regedit)
Navigate to the following entry: HKEY_CURRENT_USER\Software\REDDOXX\2.0\User
Change the value for DisableAutoDiscovery to 1.
Change the value for EnableAutoLogin to 0.
Close the registry editor and try to LogOn again.
After the successful login, you can re-activate the AutoLogin function.
This does not happen anymore by using the latest OutlookAddin, an update of the Addin is therefore recommended.