To understand the advantages of the new servicing method, you must understand how updating works for all earlier versions of Exchange. When Microsoft creates a hotfix for early Exchange products, the binary files that are included as part of the hotfix are cumulative. However, the binary files do not contain updates for the rest of the product. For example, if a hotfix contains a Store.exe file that was built on January 1, 2007, it would contain all the changes that were made to Store.exe up to January 1, 2007. However, the hotfix would not contain updated content for the Exsmtp.dll file. For Exchange 2007, each update rollup package is cumulative. For example, if you apply Update Rollup 4 on a computer that is running Exchange 2007, you receive all the fixes in that particular update package together with all the fixes that were released in all earlier update rollup packages. In this example, you receive all the updates that were released in the Update Rollup 1 through Update Rollup 4 packages.

For Exchange 2007, we have developed an integrated automated test product that is built together with the shipping product. Therefore, we can perform better integrated, end-to-end system testing than was previously possible. When we build a cumulative rollup for Exchange 2007, we build a test product together with the rollup. In this scenario, if the unified test system is successful, we are certain that the quality of the new rollup is as good as or better than what we shipped originally. This is because all the original tests must pass together with the added tests for any new fixes that are present in the rollup package.

Note:
This approach to updating does not replace service packs for the product. We still deliver additional product fixes and features in separately available service packs for Exchange 2007.

There are several changes in the Exchange 2007 update rollup packages. These changes include changes to the installer that is used, the number of files that are updated, and the file sizes. We no longer use the Update.exe installation program. Instead, we use Windows Installer technology. Also, the overall size of the installation packages and the number of files are much larger than those of individual hotfixes. The two main reasons for this are as follows:

• The packages are made up of cumulative updates.
  
• Exchange 2007 consists of lots of new, managed code.
  

Because update rollup packages are cumulative, you only have to install the latest package to bring Exchange 2007 up to date. This makes the packages larger. However, this may simplify administration of Exchange 2007. For example, you only have to deploy a single update rollup package to obtain the system stability and security improvements that are contained in many individual hotfixes.

Also, with managed code, there are many dependencies among binary files. Sometimes a single change to a core binary file requires changes to many other binary files. All the affected files must be included in the update for the particular change. Although this requirement increases the overall size of the rollup package, it also simplifies the overall Exchange environment. When Microsoft Support personnel debug Exchange, they can easily determine whether the update level is the Release to Manufacturing version (RTM), the RTM together with Update Rollup 1, and so on. This is much easier than identifying a unique set of individual updates and symbols, and it improves overall management and troubleshooting of Exchange.

Our test infrastructure guarantees that Exchange hotfixes work across multiple server roles. The order in which you apply the update rollup to the servers is not important except if you are deploying CAS-CAS proxying. Because the update rollups are not segmented for different Exchange server roles or for specific file configurations, apply each update rollup package to all Exchange 2007 servers in your environment.

If you have multiple Active Directory sites and have deployed a Client Access server in the proxy sites that do not face the Internet, apply the update rollup to the Internet-facing Client Access servers before you apply the update rollup to the non-Internet-facing Client Access servers. For other Exchange 2007 configurations, we recommend that you apply the update rollup package to the Client Access servers before you apply it to servers that are running other Exchange 2007 server roles, such as the Mailbox server role, the Hub Transport server role, and the Edge Transport server role. For more information about CAS-CAS proxying, see Understanding Proxying and Redirection.

In a production environment, Exchange 2007 is supported only on 64-bit platforms. The only exception to this is the Management Tools installation option. This option may be used on 32-bit systems to administer Exchange 2007 from a 32-bit client computer. Because customers may evaluate Exchange 2007 by using a 32-bit copy in a nonproduction laboratory environment, we provide 32-bit update rollups. However, we limit the testing of 32-bit update rollups to servers that are running the Management Tools server role.

The update process modifies Outlook Web Access directory names. Additionally, the update process overwrites any .aspx files, such as the Logon.aspx file. Therefore, you may have to re-create Outlook Web Access customizations, such as company logos, custom forms, and so on.

Microsoft releases update rollup packages approximately every six to eight weeks. The rollup packages are available on the Microsoft Update and Microsoft Download Center Web sites.

The critical fix process for Exchange 2007 resembles the critical fix process for earlier versions of Exchange.

After working with a Customer Support Specialist or with Escalation Services personnel to troubleshoot an issue, Microsoft Support personnel may escalate a request to the Exchange Customer Experience team. The Customer Experience team may fix the particular problem and give you an interim update to resolve the issue. The update is intended to support your Exchange installation until the next scheduled update rollup package is released. The interim updates benefit from much of the same testing that the cumulative updates experience. However, interim update testing is not as comprehensive as update rollup testing.

We deliver the interim update to you under your existing service level agreement. However, you must agree to remove the interim update and install the official update rollup package that resolves your problem when it becomes available. This process guarantees that your Exchange 2007 configuration returns to a known, quantifiable state.

Interim updates for Exchange 2007 are update rollup-specific. For example, an interim update that is created to fix a problem on a server that is running the release version of Exchange 2007 does not function correctly on an Exchange 2007 server that has Update Rollup 2 installed. If you receive an error message when you install an interim update, check for one of the following issues:

• You have another interim update installed.
  
• You are installing an interim update that was targeted for a different update rollup baseline
  

If you have an interim update installed on an Exchange 2007 server, you must remove the update before you install the next update rollup package. If the interim update is not removed, you may receive an error message when you try to install the next update rollup package.

Note:
You also receive an error message if you try to install an earlier update rollup package over a later update rollup package.

For more information, see the following topics: