Exchange 2010 iRule problem. Help!

The Autodiscover service working as following ways:

1. Outlook sends a Lightweight Directory Access Protocol (LDAP) query to Active Directory looking for all available SCP objects.

    

2. Outlook sorts and enumerates the returned results based on the client's site by using the keyword attribute of the SCP record. One of two lists is created, an in-site list or an out-of-site list. The in-site list provides the SCP records that have AutodiscoverSiteScope information. If there are no in-site records, an out-of-site SCP record list will be generated. The list is not sorted in any particular order. Therefore, the list is approximately in the order of oldest SCP records (based on creation date) first.

    

3. Outlook first tries to connect to each Autodiscover URL that it previously generated from either an in-site list or an out-of-site list. If that doesn't work, Outlook will try to connect to the predefined URLs (for example, https://autodiscover.contoso.com/autodiscover/autodiscover.xml) by using DNS.

    

4. If that fails also, Outlook will try the HTTP redirect method and, failing that, Outlook will try to use the SRV record lookup method. If all lookup methods fail, Outlook will be unable to obtain Outlook Anywhere configuration and URL settings.

    

According to your description, it sounds like your outlook client is using predefined URL for autodiscover service, that means when trying to access to the URL, let's say https://autodiscover.contoso.com/autodiscover/autodiscover.xml, client need to perform authentication, if your back end exchange server is configured to use NTLM, then NTLM::disable will be triggered, disabling the NTLM processing, thus authentication would fail, in turn autodiscover fails.