Where does Postbox store my profile and emails?
This is handy to know if you want to manually back up your Postbox settings and the mail stored in Postbox.
(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 7, 8 and 10
(The AppData folder is 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".)