You have deployed an antivirus solution that uses Microsoft Exchange Virus Scanning API (VSAPI) in a Microsoft Exchange Server 2010 environment.
The antivirus application running on the Microsoft Exchange Server 2010 Hub Transport server scans email messages.
The Hub Transport server performs a virus scan and stamps the email messages when they are received.
In this scenario, the background scanner unexpectedly rescans email messages on the Microsoft Exchange Server 2010 Mailbox server.
This issue occurs because the BackgroundScanningIgnoreStamp registry key is not explicitly set to 0 when the Microsoft Exchange Information Store initializes the background scanning process. The BackgroundScanningIgnoreStamp registry key set to 0 means that items that are scanned in the Hub Transport server should not be rescanned.
Note To view the BackgroundScanningIgnoreStamp registry key, locate the following subkey in the registry: