How do you fix the connection to Microsoft Exchange is unavailable Outlook must be online or connected to complete this action?

In some cases, when a new user tries to configure a connection to Exchange in Microsoft Outlook (or when a configured Outlook connects to an email server), you may receive an error: The connection to Microsoft Exchange is unavailable. In this article, we will show you how to troubleshoot and fix this error.

The action cannot be completed. The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.

The first step is to check that the Autodiscover service on the Exchange server is working correctly.

Hint. With the Exchange Autodiscover service, the Outlook client can automatically find and configure a connection to the Exchange server. You just need to enter the user’s email address and password.

You can check AutoDiscover using the following PowerShell cmdlet:

If you do not have the Exchange Management Shell installed, hold down the CTRL key and right-click on the Outlook icon in the Windows tray. Select “Test E-mail AutoConfiguration …”.

In the window that opens, specify the user’s Email address, enable the Use Autodiscover option, and click the Test button. If Exchange Autodiscover is available and configured correctly, Succeeded appears on the last line.

If you are setting up an Outlook connection to your published Exchange over Internet (client traffic comes to the corporate network from outside), you can check the correctness of the DNS settings, Autodiscover, and Exchange availability from the outside using the service.

Select Exchange Server > Outlook Connectivity, enter your email address on the Exchange server, username and password, enter captcha, and click Perform Test.

This test walks through the steps Outlook uses to connect via the Internet. It tests connectivity using both the RPC over HTTP and the MAPI over HTTP protocols.

If the computer on which you are configuring Outlook to Exchange connectivity is in one AD site, and the Exchange Server and the Global Catalog domain controller are in a different site, you must create a custom registry key on the client.

1. Open the Registry Editor (regedit.exe);
2. Go to the following registry key HKEY_CURRENT_USER\Software\Microsoft\Exchange\Exchange Provider (if this branch is missing, create it manually);
3. Add a new REG_SZ parameter named DS Server;
4. Specify the FQDN of your domain controller with the Global Catalog role as the parameter value;
5. Restart your computer and set up a new Outlook profile.

If all users are simultaneously complaining about a problem connecting to Exchange from Outlook, run the following commands in the Exchange Management Shell on a Microsoft Exchange Server with the CAS (Client Access Server) role:

Make sure all services return Success/Information responses. Verify that all URLs on the Exchange server for the OAB and Autodiscover mechanisms are configured correctly. Correct any errors found.

Then run the command:

If any of the services are down, check the status of the Exchange services. Sometimes you have to recreate IIS virtual directories.

Several more ways to fix the problem on the Outlook client side:

1. Delete default email profile in Control Panel (using Mail 32bit item), and create a new Outlook profile;
   
   
2. If RPC encryption is disabled on CAS servers, disable it in the Outlook profile settings item, and create a new profile (Encrypt data between Microsoft Office Outlook and Microsoft Exchange);
   
   
3. In older versions of Exchange, you can check for an RPC connection using the command: outlook /rpcdiag
4. Check that you can open your mailbox on the server through the browser via OWA (Outlook Web Access).

We’ve covered the top fixes and workarounds which can help you fix the “Connection to Microsoft Exchange is not available” error in Outlook 2010/2013/2016/2019.

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