Microsoft releases update rollup packages approximately every six to eight weeks. The rollup packages are available via Microsoft Update and the Microsoft Download Center. In the Search box on the Microsoft Download Center, type "Exchange 2010 update rollup" to find links to the rollup packages.

Exchange update rollups work across multiple server roles. Because the update rollups aren't segmented for different Exchange server roles or for specific file configurations, apply each update rollup package to all Exchange 2010 servers in your environment.

For Exchange 2010 configurations, the recommended order in which to apply the update rollup is as follows: Client Access server, Hub Transport server, Mailbox server, and Unified Messaging server.

If you have multiple Active Directory sites and have deployed a Client Access server in the proxy sites that aren't Internet-facing, 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 more information about Client Access to Client Access server proxying, see Understanding Proxying and Redirection.

The critical fix process for Exchange 2010 is similar to 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 specific problem and give you an interim update to resolve the issue. The interim 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 isn't as comprehensive as update rollup testing.

Interim updates for Exchange 2010 are update rollup-specific. For example, an interim update that is created to fix a problem on a server that is running the release to manufacturing version of Exchange 2010 doesn't function correctly on an Exchange 2010 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're installing an interim update that was targeted for a different update rollup baseline.
  
  

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 ensures that your Exchange 2010 configuration returns to a known, quantifiable state.

If you have an interim update installed on an Exchange 2010 server, you must remove the update before you install the next update rollup package. If the interim update isn't removed, you may receive an error message when you try to install the next update rollup package.

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

For information related to daylight saving time and time zones, see Update Your Exchange Organization When Daylight Saving Time or the Time Zone Changes.