We offer three different versions of MSG Viewer for Outlook:
App Store: MSG Viewer for Outlook Pro
App Store: MSG Viewer for Outlook (license via in-app purchase)
Website: MSG Viewer for Outlook
These versions are all functionally identical, with some subtle differences:
The reason for the 2 x App Store versions is that some individuals/organizations do not support in-app purchase for licensing. Therefore, the 'Pro' version is identical with the license pre-bundled. Apple requires unique product names for each application.
The App Store versions use sandboxing (App Store requirement), whereas, the non-App Store versions do not. This means that MSG Viewer for Outlook needs to ask for permission when saving a file in a particular folder. The "same folder as the original file" option is not available for App Store users, since it is blocked by sandboxing requirements.
It is a security vs. flexibility trade-off.
The App Store versions require the Quick Look plugin to be downloaded separately. This is due to sandboxing limitations with Apple.