Outlook Prompts for Password When Connecting to Exchange Server

The Outlook clients start to prompt for a password when connecting to Exchange Server. Entering the password will cause the prompt to reappear, creating a loop. This issue began to occur after installing a newer version of Exchange Server in the organization or following a configuration change. In this article, you will learn how to fix Outlook prompts for password when connecting to Exchange Server.

Before you start

It’s essential that you set up all the Exchange Servers the same. Therefore, if you have only one Exchange Server, troubleshooting is always easier. If you have multiple Exchange Servers, always double-check that all settings are identical between the Exchange Servers.

Step 1. Install third-party certificate

Ensure that you have a third-party certificate installed. Read more in the articles:

Step 2. Set up Autodiscover in Exchange Server

Always ensure that autodiscover is set up correctly in Exchange Server. Read more in the article Configure autodiscover URL in Exchange with PowerShell.

If you have multiple Exchange Servers and you don’t want Outlook to connect to that specific Exchange Server, ensure you null (clear) the autodiscover internal URL.

For example, you have two Exchange Servers running. One is Exchange Server 2016, and the other is Exchange Server 2019. You want to let the Outlook clients only connect to the Exchange Server 2019, then clear the autodiscover internal URL for the Exchange Server 2016.

Set-ClientAccessServer -Identity "EX01-2016" -AutoDiscoverServiceInternalUri $null

Step 3. Set up Internal and External DNS

Check that the internal and external DNS have the same URLs configured. This makes it easier when configuring the virtual directories and reduces certificate issues.

If you have multiple Exchange Servers and don’t want Outlook to connect to that specific Exchange Server, ensure you remove the Exchange Server from the DNS.

Step 4. Set up MAPI in Exchange Server

Outlook clients connect using MAPI over HTTP. This is also the preferred and default protocol in Exchange Server 2013 SP1 and later. Check that the correct MAPI configuration is enabled on the Exchange Server.

Sign in to Exchange admin center and navigate to servers > virtual directories > mapi (Default Web Site).

Check both the internal URL and external URL and ensure they use the same URL (single namespace).

Check that the following three authentication methods are selected:

• Windows authentication – Ntlm
• Windows authentication – Negotiate
• Server to server authentication (OAuth)

Suppose you want to check the MAPI virtual directory configuration using the Exchange Management Shell (PowerShell), then run the Get-MapiVirtualDirectory cmdlet.

Get-MapiVirtualDirectory | Format-List Id, Server, IIS*, Internal*, External*

The output appears.

Id                            : EX01-2019\mapi (Default Web Site)
Server                        : EX01-2019
IISAuthenticationMethods      : {Ntlm, OAuth, Negotiate}
InternalUrl                   : https://mail.exoip.com/mapi
InternalAuthenticationMethods : {Ntlm, OAuth, Negotiate}
ExternalUrl                   : https://mail.exoip.com/mapi
ExternalAuthenticationMethods : {Ntlm, OAuth, Negotiate}

To set the MAPI virtual directory.

Set-MapiVirtualDirectory -Identity "EX01-2019\mapi (Default Web Site)" -InternalUrl "https://mail.exoip.com/mapi" -ExternalUrl "https://mail.exoip.com/mapi" -IISAuthenticationMethods Ntlm, OAuth, Negotiate

Step 5. Add registry keys for Outlook

When you start Outlook on the computer, it will connect to the Exchange Server and download all the emails. Now, there’s a big chance that it’s slow with connecting.

We recommend enabling the following registry keys on the computer that has the Microsoft Outlook client installed.

Skip Microsoft 365 endpoint

Disable Outlook from connecting to Microsoft 365 to reduce AutoDiscover delays and prevent another password prompt.

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover

Create a DWORD (32-bit) Value. Give it the name ExcludeExplicitO365EndPoint and the value 1.

Read more in the article Prevent Outlook from connecting to Office 365.

Skip HTTPS root domain

Disable root domain HTTPS check to speed up connection by skipping the root domain lookup (exoip.com).

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover

Create a DWORD (32-bit) Value. Give it the name ExcludeHttpsRootDomain and the value 1.

ExcludeHttpsRootDomain

That’s it!

Read more: Outlook not connecting to Exchange after migration »

Conclusion

You learned how to fix Outlook prompts for password when connecting to Exchange Server. Ensure you walk through all the steps and adjust when a setting is not set up correctly. If you have multiple Exchange Servers, set everything up identically.

Did you enjoy this article? You may also like Automate mailbox configuration in Outlook. Don’ forget to follow us and share this article.