When you right-click an email message in the list (left side), you see the option to “Blacklist sender”, but this only blacklists a single email address. It would be much more useful to add a menu item to “Blacklist sender domain”. That way spammer domains can be blocked very easily.
Similarly, when you right-click an email address (top of the reader pane), you see the option to “Create new filter”, but this only filters a single email address. It would be much more useful to add a menu item to “Create new domain filter”. That way spammer domains can be filtered very easily.