Exchange 2010 AutoDiscover 401 unauthorized

HI

i have problem on exchange 2010 autodiscover publishing via TMG , the test rule is ok but any user try to use Autodicover externally the TMG logs shows error 401 unauthorized .

we faced this problem with external users only and i don't know if the below Blog is applicable for our case because it seems the author explain if you have this issue internal and our test commands have been tested successfully

http://clintboessen.blogspot.com/2009/06/autodiscover-issue-401-unauthorized.html

AND test result on https://www.testexchangeconnectivity.com as below

ExRCA is attempting to retrieve an XML Autodiscover response from URL https://autodiscover.xxx.com/AutoDiscover/AutoDiscover.xml for user fadi@xx.com

ExRCA failed to obtain an Autodiscover XML response.

Additional Details



An HTTP 401 Unauthorized response was received from the remote Unknown server. This is usually the result of an incorrect username or password. If you are attempting to log onto an Office 365 service, ensure you are using your full User Principal Name (UPN).

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Best Regards, Fadi.F.Haddad