Thanks for getting back.
The VSS framework is in the control of Microsoft and MS applications that don't have a dedicated VSS writer probably don't need one. Even though there is no specific VSS writer for Outlook, the file system is 'flushed' and any uncommitted NTFS cached writes will be written to disk. This is actually better than simply losing power and Outlook .pst files will maintain transactional consistency.
My file backups are small enough that I can eyeball the modified dates of Reflect's "Files backed up" log, or my robocopy log. It seems that any files whose modified dates are within a few seconds of the time a snapshot happens are at risk of inconsistency and need to be reviewed.
Having a modified time stamp at the time of the snapshot does not indicate that there are any inconsistency issues at all. Most (all modern) applications will handle 'crash' consistent termination without loss of data.
EDIT: Is it possible that ANY file written by a non-VSS-aware application could be in an inconsistent state even if it's a file that has no relationship to any other file? Presumably VSS pauses while in-progress file system activity completes, so that file system indexes and so forth are in a consistent state, but what of an application that performs several sequential writes in order to make a single "logical" change? That isn't really different than updating several coordinated files, and so couldn't a crash during this process, or a snapshot taken during this process, be "corrupt" in the sense of leaving a file in an unintended state?
It is possible for a poorly written, non VSS aware application that uses it's own database format and makes no attempt for atomic transactional writes to be inconsistent after power failure or snapshot. This won't be a modern or serious application though.
The MS VSS framework does a great job of ensuring that snapshots of a running system are in a consistent and clean state, however, If you are running applications that are not VSS aware and that can irreparably 'break' due to power failure then you might want to consider whether to let them run during snapshot creation.
Nick - Macrium Support