Remove Temporary Attachment Files on Exit on macOS
On macOS, if you open an attachment in a helper application (like Preview, iWorks, etc.), Postbox will not delete that temporary file on exit. If you want the temporary file to be removed on exit, you need to set a hidden pref.
- Open the config editor.
- Right click in the Config Editor and from the context menu, choose New | Boolean.
- Enter a preference name of browser.helperApps.deleteTempFileOnExit and select OK
- Select true as the value for this preference.
The next time you open an attachment in Postbox, that temporary file will be deleted on exit.