Deploy and install Dynamics 365 App for Outlook

Step 1: Set the default synchronization method [Assume done]

Step 2: Test email configuration and enable mailboxes [Done]

Step 3: Provide security role access [Done]

The security role Dynamics 365 App for Outlook User is available from build 9.1.0.4206 or later. If a user doesn't have this security role or its underlying privileges, they'll receive the following error: You haven't been authorized to use this app. Check with your system administrator to update your settings. You must add users to this role so they can use Dynamics 365 App for Outlook. This will ensure that the users have the basic privileges needed to access App for Outlook.

Step 4: Install App for Outlook

Follow these steps to push Dynamics 365 App for Outlook to selected users, all users, or have users install it themselves as needed.

Step 4.1: Push the app to your users

1. To push the app to your users, from your app, go to Settings > Advanced Settings.

2. Go Settings > Dynamics 365 App for Outlook.

3. The Getting Started with Microsoft Dynamics 365 App for Outlook page lists all eligible users that can use App for Outlook. You have several different options on how you can deploy the app to your users.

4. Etc.

Or

Step 4.2: Have users install App for Outlook themselves

1. From your app, go to Settings > Advanced Settings.

2. Select the Settings button Settings button., again and then select Apps for Dynamics 365 apps.

3. In the Apps for Dynamics 365 apps screen, under Dynamics 365 App for Outlook, users select Add app to Outlook.

https://learn.microsoft.com/en-us/dynamics365/outlook-app/deploy-dynamics-365-app-for-outlook