Outlook for Windows Doesn't Open After Adding a MAPI Account

Occasionally, when adding a MAPI account to Outlook for Windows, when you open Outlook you're presented with this:

This is because Outlook defaults to disabling "Cached Exchange Mode" for a new mail account. Cached Exchange Mode allows you to work with your Exchange account in situations where a network connection is either very slow or not available at all. Microsoft even recommends using Cached Exchange Mode for Microsoft 365 mail accounts or when using Exchange Server. The simplest way to enable Cached Exchange Mode for an account is the following:
  1. In the Windows search box in your taskbar, type "Control Panel".
  2. Then, select Control Panel from the search results.
  3. In the Control Panel search box, type "Mail".
  4. Select Mail (Microsoft Outlook), and it opens the Mail Setup - Outlook dialog
  5. Click on Email Accounts... and then select the specific account you need to modify. (If there are more than one.)
  6. After selecting the account, click the Change... button.
  7. This opens up the Change Account dialog. Here, you'll see the account's Server Settings. In the Offline Settings area, make sure "Use Cached Exchange Mode" is checked. If not, check it.
  8. Click the Next button, then the Finish button and you're done.
You should now be able to open Outlook and the account will load.