A new feature is available that enables Outlook 2007 to use DNS Service Location (SRV) records to locate the Exchange Autodiscover service

This article describes a new feature in Microsoft Office Outlook 2007. This new feature enables Outlook 2007 to use DNS Service Location (SRV) records to locate the Exchange Autodiscover service.

Update Information

A supported feature that modifies the default behavior of the product is now available from Microsoft, but it is only intended to modify the behavior that this article describes. Apply it only to systems that specifically require it. This feature may receive additional testing. Therefore, if you are not severely affected by the lack of this feature, we recommend that you wait for the next Outlook 2007 service pack that contains this feature.

To obtain this feature immediately, download the feature by following the instructions later in this article or contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
This feature is available as part of the following update rollup for Outlook 2007:

Background

When Outlook 2007 is not domain-joined, you have to use a predefined URL method or an HTTP redirect method in order to locate the Autodiscover service. The following list contains two predefined URL methods and one HTTP redirect method:

• https://<smtpdomain>/Autodiscover/Autodiscover.xml
• https://autodiscover.<smtpdomain>/Autodiscover/Autodiscover.xml
• http://autodiscover.<smtpdomain>/Autodiscover/Autodiscover.xml

Note The predefined URL method requires that you have a valid SSL certificate for the URL that you are using. This method can be difficult to implement because you generally use one DNS name for the Outlook Anywhere feature for Microsoft Exchange Server 2007 and a different DNS name for Microsoft Office Outlook Web Access.

Note The HTTP redirect method can be difficult to implement because it requires the following in order to work correctly:

• An additional Web site in IIS
• Two Public IP addresses

By using the software update that is described in this article, Outlook 2007 will perform an additional check for a DNS SRV record in order to locate the Autodiscover service. This additional check does not require complex configuration or a valid certificate for the Autodiscover service.

How to use the new DNS SRV lookup method to locate the Exchange 2007 Autodiscover service

To use the new DNS SRV lookup method in order to locate the Exchange 2007 Autodiscover service, follow these steps.

Note You must create the Autodiscover SRV record in the external DNS zone that matches the right side of your user's SMTP addresses. For example, if a user's primary SMTP address is user@contoso.com, the record must be created in the contoso.com external DNS zone. If you have multiple primary SMTP address domains in your organization, you must create an Autodiscover SRV record in each zone.

1. In your external DNS zone, remove any HOST (A) or CNAME records for the Autodiscover service.
2. Use the following parameters to create a new SRV record:

   Service: _autodiscover
   Protocol: _tcp
   Port Number: 443
   Host: mail.contoso.com
   

   Note For more information about how to create this record, see the "About SRV records" section.

Note In this example, mail.contoso.com is a name for which your certificate is valid. Usually, this is the same DNS name that you use for Outlook Anywhere and for Outlook Web Access.

In this example, the Autodiscover service does the following when the client tries to contact the Autodiscover service:

1. Autodiscover posts to https://contoso.com/Autodiscover/Autodiscover.xml. This fails.
2. Autodiscover posts to https://autodiscover.contoso.com/Autodiscover/Autodiscover.xml. This fails.
3. Autodiscover performs the following redirect check:
   GET http://autodiscover.contoso.com/Autodiscover/Autodiscover.xml
   This fails.
4. Autodiscover uses DNS SRV lookup for _autodiscover._tcp.contoso.com, and then "mail.contoso.com" is returned.
5. Outlook asks permission from the user to continue with Autodiscover to post to https://mail.contoso.com/autodiscover/autodiscover.xml.
6. Autodiscover's POST request is successfully posted to https://mail.contoso.com/autodiscover/autodiscover.xml.

About SRV records

If you are using Windows DNS, the steps to create an SRV Record are as follows:

1. Open the DNS Management MMC snap-in.
2. Expand Forward Lookup Zones.
3. Locate and right-click the external DNS zone, and then click Other New Records.
4. Click Service Location (SRV).
5. Enter the parameters by using the required values.
6. Click OK.

Note Depending on your DNS solution, you may be unable to implement SRV records. Contact your DNS hosting provider or your DNS administrator for guidance.