1. Use the Remote Connectivity Analyzer via https://www.testexchangeconnectivity.com/ to test the Outlook Autodiscover. The screenshot below is for your reference:
2. Expand All the results and search the <Server>(for example: firstname.lastname@example.org) and <PublicFolderServer>
3. Manually set up Outlook to connect to Exchange Online. To do this, follow these steps:
- Click Start, click Control Panel, and then click Mail.
- Click Show Profiles and then click Add.
- Type a name for the profile, and then click OK.
- Click to select the Manually configure server settings or additional server types check box, and then click Next.
- Click Microsoft Exchange, and then click Next.
- In the Server box, type the host address that you noted in step 2 <Server>.
- Make sure that the Use Cached Exchange Mode option is selected.
- In the User Name box, type your full name (for example, John Smith), and then click More Settings.
- Click the Connection tab.
- Make sure that the Connect to Microsoft Exchange using HTTP check box is selected, and then click Exchange Proxy Settings.
- In the Use this URL to connect to my proxy server for Exchange box, type the host address that you noted in step 2 <PublicFolderServer>.
- Make sure that the Only connect to proxy servers that have this principal name in their certificate check box is selected, and then type msstd:outlook.com.
- Click to select the On fast networks, connect using HTTP first, then connect using TCP/IP check box, and then click to select the On slow networks, connect using HTTP first, then connect using TCP/IP check box.
- Under Proxy authentication settings, click Basic Authentication.
- Click OK.
- Click the Security tab.
- In the Logon network security dropdown-list, select Anonymous Authentication.
- Click OK.
- Click Check Names. When the server name and the user name are displayed with an underline, click Next.