"We can’t load this app because your email account isn’t configured with Dynamics 365 server-side sync for incoming email..." error occurs in Dynamics 365 App for Outlook

When attempting to open the Dynamics 365 App for Outlook, you encounter the following error:

"We're sorry

We can’t load this app because your email account isn’t configured with Dynamics 365 server-side sync for incoming email. Ask your system administrator to set up server-side sync for incoming email."

If you click Show more, you see additional details such as the following:

"Error: Email account isn't configured with server-side synchronization for incoming email Trace: Error: Email account isn't configured with server-side synchronization for incoming email"

The Dynamics 365 App for Outlook requires Server-Side Synchronization to be enabled for your mailbox. This error occurs when your mailbox in Dynamics 365 is not enabled for incoming email using Server-Side Synchronization. 

NOTE: Your mailbox needed to have had Server-Side Synchronization configured correctly before the app could be deployed to your mailbox. However, if the status of your mailbox in Dynamics 365 changes later to a failure status, you would encounter this error until the mailbox is correctly configured and enabled again.

Verify your mailbox is enabled for incoming email with Server-Side Synchronization.

1. Access Dynamics 365 as a user with the System Administrator role.
2. Navigate to Settings and then click Email Configuration. 
3. Click Mailboxes and then change the view to Active Mailboxes. 
4. Locate and open the mailbox record for the user encountering the error.
5. Verify the Incoming Email option is set to Server-Side Synchronization or Email Router. If the app will also be used to track Appointments or Contacts in Outlook, verify the Appointments, Contacts, and Tasks setting as well.
6. If the Incoming Email Status does not already show as Success, click Test & Enable Mailbox and make sure to select the checkbox that appears in the dialog. 
7. If the mailbox tests do not succeed, review the messages in the Alerts section. If an alert includes a Learn More link, click this link for additional details. If you continue to see failures after clicking Test & Enable Mailbox, click here for additional guidance.
8. After the mailbox shows Success for Incoming Email Status, close and reopen Outlook. Then try to open the Dynamics 365 App for Outlook again.