This article applies to:
Windows Server 2012 R2, Exchange 2016

PROBLEM
When you run the ConfigureEnterprisePartnerApplication.ps1 on your Exchange server in order to configure application partnership with another server (typically Skype for Business or SharePoint) you receive the following error message:

Cannot acquire auth metadata document from ‘https://sfbpool.company.com/metadata/json/1’. Error: The remote server returned an error: (503) Server unavailable.

When you attempt to open the mentioned URL via browser, you are able to open it and you receive the configuration data:

CAUSE

The most usual cause for this error is wrong proxy configuration. Exchange server does not take the proxy configuration from the IE browser. This setting can be configured in 2 places: Windows server OS or the Exchange itself.

SOLUTION

Windows proxy settings:

Exchange will by default take over this value for proxy (unless proxy is explicitly defined in Exchange itself)

To see current proxy configuration in Windows, open the command prompt and type the following command:

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To remove the proxy settings for direct access you can use the following command:

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To use the same settings as defined in Internet Explorer web browser:

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To set correct proxy and at the same time exclude local domain:

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Note: The proxy port number is usually 8080, but can be different in your environment.

Exchange Proxy Settings

Exchange will by default take the proxy value from the Windows OS (as described above). If you want to configure proxy settings for Exchange server application only you can do that via Exchange PowerShell:

In order to see the current proxy configuration on all your Exchange servers, use the following PowerShell command:

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To remove the proxy configuration from all your Exchange Servers:

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Dejan Foro