How to keep OST files in Veeam Agent backup

Challenge

When you create a backup using Veeam Agent for Microsoft Windows, Microsoft Volume Shadow Copy Service (VSS) excludes certain files like deleted, temporary, paging or OST files from the backup scope.
 

Cause

Veeam Agent for Windows uses Microsoft VSS for backup operations. Microsoft VSS automatically excludes certain temporary files, such as the OST files, from VSS snapshot operations. These exclusions are controlled by the FilesNotToSnapshot registry key. To learn more, see this Microsoft Docs article.

Solution

You can edit or delete subkeys of the FilesNotToSnapshot registry key to include automatically excluded files in the backup. For example, to include OST files, do the following:

1. Open Registry Editor (click the Start button, select Run, enter regedit in the Open: box and select OK).
2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshot registry key.
3. Delete the OutlookOST subkey.

Keep in mind that the OST files exclusion is recommended by Microsoft. To learn more about the recommendation, see this Microsoft Tech Community article.