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Outlook can't connect through a proxy that's set up by using a file://-based PAC file

Original KB number:   2332495


Assume that you have a proxy that's set up by using a file://-based PAC file. In this situation, you can't use Outlook Anywhere to connect through this proxy to an on-premises Exchange 2013 server, an on-premises Exchange 2010 server, or Exchange Online.


WinHTTP does not support PAC URLs that use a file:// prefix. Therefore, when Outlook connects by using WinHTTP, it can't use the PAC file if the URL starts with file://. This behavior is by design.

Workaround - Method 1

Set up an http://-based PAC file, select the Use automatic configuration script option in Internet Explorer, and then specify the URL of the PAC file in the Address box.

Workaround - Method 2

Deploy Web Proxy Automatic Discovery (WPAD), and then select the Automatically detect settings option in Internet Explorer.

For more information, see Automatic discovery for firewall and Web Proxy clients.

More information

For more information about WinHTTP autoproxy support, see WinHTTP AutoProxy support.

For more information about a similar scenario in Skype for Business Online (formerly Lync Online), see Lync 2013 or Lync 2010 can't connect to the Skype for Business Online service because a proxy is blocking connections from MSOIDSVC.exe.

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