Configuration and General Troubleshooting
1. Open the mailbox record and click the Alerts section.
2. Look for any errors and review the message that is displayed.
If no errors appear, navigate to Settings, Email Configuration, and then Email Configuration Settings. In the Configure alerts section, verify the Error option is selected. If this was not already selected, enable this option and click OK. Then click the Test & Enable Mailbox button again and check for any errors. When performing the Test & Enable action, also make sure to select the checkbox that appears in the dialog.
3. Click the Learn more link if it appears. If there is an article designed to help with that specific error, this link will direct you to it.