Biff/extension for unread mail

I recently switched from XFCE to Gnome (on D13). I previously relied on the Mail Watcher XFCE plugin/biff, which provides a visual tray icon for unread mail in a configured list of IMAP/S folders.

I'm struggling to find a useful alternative for Gnome. The ones I've tried are often only a proxy for the MUA's notifier, notify only of new mail rather than of unread mail, display obtrusive pop-ups, or scan only the Inbox.

Any pointers?