When your Nine app needs a permission to access your company's Exchange server...
First of all, you have to get the help of Active Directory administrator in your company when you meet a message like requesting to change server's setting.
That is, you should change the value of "Users can consent to apps accessing company data on their behalf" to Yes in the Active Directory settings. Therefore, you need to request to change the follows.
1. Connect to https://portal.azure.com as the admin account. In most cases, you need to ask your server admin to change the following settings.
2. Select the following path in the portal.
2.1. Azure Active Directory > Users > User settings > Enterprise applications / Manage how end users launch and view their applications
2.2. Enterprise applications - User can consent to apps accessing company data on their behalf - Select 'YES'