Basically the "Sandbox" is a security measure of macOS which restricts the things an application can do. This new architecture has some consequences:
- Posterino needs your permission to access specific locations on your hard disk.
- Therefore on opening a saved document, Posterino may ask you for permission to access parts of your hard disk. Posterino needs this permission to access the image files used by the document in question.
- To simplify your workflow, you can grant Posterino access to specific locations of your hard disk using the preferences at > > . This way Posterino wont ask you ever and ever again for permission to a given location.