Quickly Attach Documents to a New Message in macOS
A common request is to be able to attach documents created in Microsoft Office and iWork using their built-in Share functions. Here is a workaround that allows Postbox users on macOS to attach their documents instantly:
First, make sure the document is saved. Then, in the title bar at the top of the document window, drag and drop the document icon onto the Postbox icon in the Dock.
Postbox will respond by composing a new message with the file attached. This works in Microsoft Office, iWork, Adobe Reader, and Preview.
Note: The Postbox application must be running when this operation is performed.