Ok i tested eM Client V10.3.4341 (up coming version) and Windows 11 25H2 you actually “don’t need to enable Use System Notifications in eM Client” to get the badge new mail icon to show as per my example below. Just enable “Show badges on taskbar apps” in the OS Taskbar Behaviours and then “minimize eM Client”.
If your happy to test this new version, backup your current version first via “Menu / Backup” and then once backed up "close eM Client and download the Windows version via the link above and install. You can see when the backup is complete in Show Operations via the dropdown on the right of Refresh top left.
