Outlook Backup: .ost files are not being backed up
Problem Description
Outlook .ost files are not backed up by Backup ONE and are not included in the backup archive (with or without error message).
The background:
.ost files are designed by Microsoft by definition not to be backed up because they are considered merely copies of the original data (on the server), while .pst archives represent the actual main archive. Therefore, Windows actively prevents the creation of shadow copies of .ost files through a registry entry (more on this in the solution section below). When Outlook starts, it locks the files exclusively, and the backup program cannot read the file while Outlook is running (Note: often the service continues running in the background even when Outlook appears to be closed, and the file remains locked).
More on this topic in the Microsoft Technet/Community forum:
Solution
The common solution for this is to manually delete the registry entry that prevents the creation of shadow copies of .ost files.
- Open the Registry Editor (Start -> Run -> regedit.exe)
- Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshot
- Delete the subkey OutlookOST (green):
- Create a backup now. The .ost file should now be included in it.
Alternatively, you can close Outlook each time before the backup starts. However, you must ensure that Outlook is not running in the background and continues to lock the file.