The Short Story

Last Friday, we released an update to Microsoft Office Outlook 2007 that will help to address some performance issues that are discussed in Knowledge Base Article 932086. You can find a description of the update and a link to the appropriate download page for your version of the update in Knowledge Base Article 933493.


(Users of the Business Contact Manager features of Outlook should see the note at the end of this post about a separate update that should be installed first.)


The Long Story

We’ve been investigating some reported performance problems with Microsoft Office Outlook 2007 for some time. Our investigations revealed that these specific performance problems affected users who had large mailbox files (.pst and .ost files) stored on their computers.


As part of our continued effort to improve our customers’ product experiences, on Friday we released an update to Microsoft Office Outlook 2007 that addresses these specific performance problems. You can find a link to the update below (or above, for that matter).


Some of these performance problems have been discussed in external blogs and other forums written by our customers. We certainly appreciate learning about everyone’s individual experiences with the product. We hope that this update will address many of the performance problems that people have noticed. As of today, the update has already been downloaded by more than 12,000 times by people around the world. 


This particular update includes several performance improvements rolled into one patch. It’s designed to improve the general responsiveness of Outlook during common operations including reading, moving, deleting, and downloading e-mail messages for users who have large mailbox files. For those out there who care about the technical details, there are two specific changes are worth mentioning:

  • We improved our handling of large table data structures inside of the Outlook storage subsystem. “Large tables” are created whenever a user has tens of thousands of items in a single folder, and they are also created by our search index infrastructure which is new for Outlook 2007. It’s important to note that this is NOT a problem with the search indexing mechanisms for Windows XP or Windows Vista. Rather, it’s a change to the way Outlook stores data that lets Outlook use the index efficiently.
  • We made some changes to the way we handle data replication information in PST and OST files.

It’s important to note that these changes do NOT change the format of either .pst or .ost files. There is no need to rebuild these files, and files created with this updated version of Outlook are backwards-compatible with previous versions of Outlook.


Customers who install this update may notice generally improved performance and responsiveness when Outlook is reading or writing data. Examples of these improvements include:

  • An improvement in speed when opening and reading messages
  • A decrease in the amount of time it takes to copy or move messages from one folder to another.
  • A decrease in the amount of time it takes to delete messages.
  • An increase in the download speed when downloading messages from the Exchange Server.

This update was specifically designed to address performance problems which occur with large mailbox files, but you may see an improvement in performance with this update even if your mailbox file isn’t “large” due to the specific data in your mailbox. Our efforts in analyzing the performance of Outlook are continuing, even after these changes.


As I mentioned above, we appreciate hearing about the experiences of our customers and we certainly hope that this update improves your experience with Outlook 2007.


Here are some links to the important information:

I do hope that this update improves your experience with Outlook 2007!