TMG 2010 - Autodiscover fails on Exchange 2010

Hi guys,

 I'm having trouble with the autodiscover feature in Exchange 2010, users can't setup Outlook from outside the domain network.

I ran the Microsoft Connectivity Test and it failed:


Our mail server is behind Forefront TMG 2010, but that path is published.


I don`t understand why TMG is blocking connections to that URL if it`s published on the rule.


Any help would be appreciated.

Regards.