Microsoft built into Outlook 2007/2010 a nice way to test Outlook AutoConfiguration.  This can be a very helpful tool to check to see what settings are being applied to Outlook for connecting to an Exchange organization.  Below are the steps to use this tool and some help with analyzing the results:

1.  Outlook needs to be running to launch the AutoConfiguration tool.

2. To launch the tool locate the Outlook icon in your system tray (this is the area by the date and time in the taskbar, normally on the lower right side of the screen).  You might need to select the up triangle to locate the hidden icons.

3. Hold down the Ctrl key and right mouse click on the Outlook icon

4. Select the Test E-mail AutoConfiguration menu item

5. Your email address should be listed, un-check Use Guessmart and Secure Guessmart Authentication and click on Test (to test for another email address enter it as well as the password for that account)

6. Above are the results from the test when I ran it against my company email account from internal to our network.  If you have Outlook Anywhere (RPC over HTTPS) enabled in your environment or are utilizing Office 365 then I recommend running this test external to your network as well.  You can also utilize this site, https://www.testexchangeconnectivity.com/ to test connectivity for Exchange on-premises and Office 365.

So what are we looking at above?  in the first two screen shots I am displaying the output from the Results tab.  These two shots show the settings that are being applied to my Outlook configuration for connecting to my company’s Exchange Organization.  The top one shows the  Protocol: Exchange RPC settings, these are the settings that will be used when I am local to my company’s network.  The second one shows the Protocol:Exchange HTTP, these are the settings used for Outlook Anywhere when I am external to my company’s network.  Review these settings and ensure the proper Server names and URLs are being applied to the client.

The last screen shot above is showing the output from the Log tab.  If you have no output in the Results tab this is where you can trace how the Outlook client attempts to locate the Autodiscover service for your Exchange organization.  If Outlook cannot contact the Autodiscover service then it cannot determine the settings to be applied.  The second line shows a URL that is found from Active Directory since I ran this internal to my network, the SCP or Service Location Point.  The SCP is set my the Exchange Admin for your organization to make Autodiscover easily found when in the domain.  If I had run this external to my network, it would go through a progression of trying URLs based on my email domain (will add this later tonight from home).

So use this tool to help troubleshoot problems with connectivity to Exchange, it is a great tool and I use it often when doing Exchange migrations.  It is also helpful to troubleshoot authentication pop ups.  These sometimes happen not for connecting the client to the mailbox but for things like Offline Address Book (OAB) download.  So if you get authentication pop ups randomly check the URLs for OOF, OAB and Unified Messaging and ensure they are properly configured.  If these URLs are not configured properly then Outlook might connect and be able to send and receive email just fine, but have other issues.

Hope this helps you out!