To use Outlook Web App Web Parts, you must, at a minimum, be delegated
"Reviewer" access to the content that you're opening. If you've
embedded an Outlook Web App Web Part that requires authentication into
an application, you must pass authentication information through
together with the request for the Web Part. One way to do this is by
configuring the Outlook Web App virtual directory to use Integrated
Windows authentication. Integrated Windows authentication lets users
who've already logged on by using their Active Directory account use
Outlook Web App without having to enter their credentials again.
from this you get:
You can configure Integrated Windows authentication for Outlook Web
App in Microsoft Exchange Server 2010. Integrated Windows
authentication enables the server to authenticate users who are signed
in to the network without prompting them for their user name and
password and without transmitting information that isn't encrypted
over the network.
Integrated Windows authentication can be set only on Exchange 2010
virtual directories on an Exchange 2010 server that has only the
Client Access server role installed. Integrated Windows authentication
can be set on any Outlook Web App virtual directory on an Exchange
2010 server that has both the Client Access and Mailbox server roles
based on this info:
in shell command:
Set-OwaVirtualDirectory -Identity "owa (Default Web Site)" -WindowsAuthentication <$true|$false>
1.In the console tree, locate the virtual directory that you want to configure to use Integrated Windows authentication by using the
information in step 2 or step 3.
2.Select Server Configuration, select Client Access, select the server hosting the Outlook Web App virtual directory, and then click the
Outlook Web App tab.
3.In the work pane, select the virtual directory that you want to configure to use Integrated Windows authentication, and then click
4.Click the Authentication tab.
5.Select Use one or more standard authentication methods.
6.Select Integrated Windows authentication.
more details on the above can be found here, http://technet.microsoft.com/en-us/library/bb430796(v=exchg.141).aspx as to your question.
Your currently using forms based authentication from the webpart. Even tho you have intergrated authentication setup on sharepoint server and on exchange it will divert to forms based auth (somthing todo with how the webpart calls the server and directory restrictions).
So you talk about access directly from the url, yes it might be setup to use intergrated win auth on exchange hence why you can access directly without a login and see, but the webpart connecting to the server needs to handshake regardless of you credentials unless its been set to have access via the virtual directory that is explicitly set to allow windows intergrated authentication!
so currently in your webpart its performing a double login, even tho your logged in to the current machine that is used for sharepoint, exchange still asks for a login request (forms authentication) to request the information from the virtual directory on exchange server!
This is why you need to goto exchange and goto the virtual directory, then change the authentication on that specific directory to intergrated windows authentication
when i talk about authentication on a virtual directory im refering to this:
as you can see the above is using forms based, check your ows directory authentication type!