Where does Postbox store my data and emails?
This is handy to know if you want to manually back up your Postbox settings and the mail stored in Postbox.
macOS
~/Library/Application Support/PostboxApp
(In macOS the Library folder is hidden. To access it, open the Finder, hold the Option key, then select Library from the Go menu.)
Windows 8 and higher
Users\username\AppData\Roaming\PostboxApp
(The AppData folder is a hidden folder; to show hidden folders, open a Windows Explorer window and choose "Organize → Folder and Search Options → Folder Options → View (tab) → Show hidden files and folders".)
NOTE: The data folders for Postbox 5 and below is named "Postbox" instead of "PostboxApp," but it is stored in the same locations.