When Outlook attempts to retrieve Autodiscover information from your Microsoft Exchange server, you may experience unexpected results if you are using one or more of the available registry values that can be used to control Autodiscover.
When Outlook tries to contact the Autodiscover service on the Exchange server with the Client Access Server (CAS) role it can use several different methods to reach the service, depending on the client-server topology. The currently implemented methods used by Outlook are:
HTTPS root domain query
HTTPS Autodiscover domain query
Local XML file
HTTP redirect method
SRV record query
Cached URL in the Outlook profile (new for Outlook 2010 version 14.0.7140.5001 and later versions)
Direct Connect to Office 365 (new for Outlook 2016 version 16.0.6741.2017 and later versions)
By default, Outlook will attempt one or more of the above methods if it is unable to reach Autodiscover. For example, in a scenario with a machine not joined to a domain Outlook will try to connect to the predefined URLs (for example, https://autodiscover.contoso.com/autodiscover/autodiscover.xml) by using DNS. If that fails, 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.
Please see the Exchange Autodiscover Service White Paper appropriate for your version of Exchange for details on all of the different Autodiscover connection methods used by Outlook.
In some scenarios, however, you may want to use Autodiscover-related registry/policy values to control the method(s) used by Outlook to reach Autodiscover. However, if you configure the Autodiscover registry/policy values incorrectly, you may prevent Outlook from obtaining Autodiscover information.
To resolve this problem, please review the Autodiscover-related registry data you may have on your Outlook client to ensure the data is configured correctly. Also, if you are unsure if the registry data is needed, consider changing the data for any of these registry values to zero (0) and then test Outlook to see if you experience a difference in Autodiscover.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Start Registry Editor.
In Windows 10 and Windows 8, press the Windows Key + R to open a Run dialog box. Type regedit.exe and then press OK.
In Windows 7, click Start , type regedit in the Search programs and files box, and then press Enter.
Locate and then select the following registry subkey:
Notex.0 in the above registry path corresponds to the Outlook version (16.0 = Outlook 2016, 15.0 = Outlook 2013, 14.0 = Outlook 2010, 12.0 = Outlook 2007).
Review the following possible values that may be located under the \Autodiscover subkey.
ExcludeLastKnownGoodURL (only applies to Outlook 2010 version 14.0.7140.5001 and later versions)
ExcludeExplicitO365Endpoint (only applies to Outlook 2016 version 16.0.6741.2017 and later versions)
Note Some documentation states that the ExcludeSrvLookup value is used by Outlook in this scenario. Unfortunately, this documentation is incorrect as the ExcludeSrvLookup value does not exist in Outlook code. Only the ExcludeSrvRecord registry value is used by Outlook to control the SRV record lookup for Autodiscover. Therefore, if you find a value called ExcludeSrvLookup under the \Autodiscover subkey, you can safely change its value to 0.
Repeat step 3 using the following registry subkey:
Note x.0 in the above registry path corresponds to the Outlook version (16.0 = Outlook 2016, 15.0 = Outlook 2013, 14.0 = Outlook 2010, 12.0 = Outlook 2007).
You can use the following steps in Outlook to determine the method by which Outlook is attempting to retrieve Autodiscover information from Exchange.
Press the CTRL key, right-click the Outlook icon in the notification area, and then click Test E-mail AutoConfiguration.
Verify the e-mail address is correctly entered in the E-mail Address box.
Enter your password if you are not logged into a domain or if you are accessing a mailbox that is different from your mailbox.
Click to clear the Use Guessmart and the Secure Guessmart Authentication check boxes.
Review the details on the Log tab.
The following figure shows the Log tab when the ExcludeScpLookup and ExcludeHttpsAutoDiscoverDomain values have been set to 1.
Compare this information when only the ExcludeScpLookup value is set to 1.
Note Ignore the failures in the above figures as this information is only intended to show you the different lookup attempts made by Outlook.
Also, if you enable logging in Outlook (2007 or 2010), the different Autodiscover lookup attempts can be found in the %temp%\Olkdisc.log file. This log file also includes any registry settings you have configured to exclude any of the Autodiscover lookup methods. In the following figure, you can clearly see that the ExcludeScpLookup and ExcludeHttpsAutoDiscoverDomain values are both set to 1.
Please see the following article related to the client-side management and administration of Autodiscover.