"Delayed write failed" error message when .pst files are stored on a network file server that is running Windows Server 2008 R2

Applies to: Windows Server 2008 R2 Service Pack 1Windows Server 2008 R2 DatacenterWindows Server 2008 R2 Enterprise


Consider one of the following scenarios: 

Scenario 1:
  • You enable Remote Desktop on a computer (computer A) that is running Windows 7 or Windows Server 2008 R2.
  • You configure an Outlook 2010 client that is installed on computer A to save Personal Folder (.pst) files on another computer (computer B). Computer B is a file server that is running Windows Server 2008 R2.
  • You establish a remote connection to computer A from a client computer, and then start Outlook 2010 in the Remote Desktop session.
In this scenario, you receive the following error message that states that the .pst file is corrupted:
Delayed Write Failed
Windows was unable to save all the data for the file file path. The data has been lost. This error was returned by the server on which the file exists. Please try to save this file elsewhere.
Additionally, the following event is logged in the System log on computer A:Note This issue does not occur if you disable the Server Message Block version 2 (SMBv2) file sharing protocol on the file server.

Scenario 2:

  • You have mapped a network drive to a server share and you use offline files to make the data on this share available offline.
  • You have a MUP filter driver installed (e.g. disc encryption Software).
  • You try to open a file (e.g. a text file) of a given size from this share while you're connected to the Network, although the actual SMB Connection to the server is not yet established.

In this Scenario, you might get the this error message:

  Cannot open the %% file. Make sure a disk is in the drive you specified

If you click on OK the text file will be empty. If you now close and open the file again it might work.


Scenario 1:
This issue occurs because the Outlook 2010 client tries to write data to an open SMBv2 file ID that has read-only access.

Scenario 2:
This issue occurs because the offline files client tries to read the file from the server before the actual SMB connection is established.


To resolve the issue, install the hotfix on the computer that Outlook 2010 is installed on (computer A) respectively on the Computer that Encounters the error while opening the file.

Note This update also fixes a regression issue in the Rdbss.sys file after the update 2775511 is installed. Install this update (2732673) after you install update 2775511. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
2775511 An enterprise hotfix rollup is available for Windows 7 SP1 and Windows Server 2008 R2 SP1

Microsoft Catalog

This hotfix is available at Microsoft Update Catalog.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must be running 7 Service Pack 1 (SP1) or Windows Server 2008 R2 Service Pack 1 (SP1). For more information about how to obtain a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To apply this hotfix, you do not have to change the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates