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Slow performance with Microsoft Outlook when Opening emails or switching between folders
Technical Articles ID:   KB86832
Last Modified:  8/11/2017


McAfee VirusScan Enterprise (VSE) 8.8 (all patched and unpatched versions)

Microsoft Outlook (all supported versions)


Opening emails or switching between folders in Outlook results in longer than normal wait times when VSE 8.8 is installed and the Email Scanner component enabled.


Although this appears to be caused by the VSE Email Scanner, a Windows Performance Recorder Trace of the node reveals excessive wait time being consumed by Microsoft MSO.DLL.

MSO.DLL attempts to use Exchange Autodiscover, but the Autodiscover infrastructure is incorrectly configured, resulting in slow performance. Adding the VSE email component only highlights the problem.

NOTE: Autodiscover is the mechanism used by Outlook to find the appropriate Exchange server. If Autodiscover is incorrectly provisioned, it can cause Outlook functionality to be dramatically impacted.


This issue is not caused by VSE 8.8. Microsoft has indicated that correcting the Autodiscover provisioning alleviates this problem.

McAfee cannot provide advice about how to configure Exchange Autodiscover. You must contact Microsoft Technical Support for assistance to identify the cause of the excessive wait time consumed by Microsoft MSO.DLL. McAfee recommends that you obtain a Windows Performance Recorder Trace of the node to verify the issue is related to wait time being consumed by Microsoft MSO.DLL. If it does not, contact McAfee Technical Support using the details provided in the Related Information section below.

To learn more about Autodiscover provisioning, see https://msdn.microsoft.com/en-us/library/office/jj900169%28v=exchg.150%29.aspx or contact Microsoft Support.

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