This way, you specify different actions for less important folders, or no action at all.
Due to the individual folder (or filter) settings, the plugin is configurable with a right-click on an account or folder, not in the main preferences window. Please read https://tjeb.nl/Projects/Mailbox_Alert/Manual/ for more information and examples.
Additionally, while I haven't spent much time on it lately, please send bug reports to me directly. A negative review is fine, but I cannot engage to get bugs fixed through reviews :)