See @Gary thread post below to show new mail notifications in the Windows tray for Windows 10. Windows 11 is pretty much the same except slight different enabling the tray icon.
https://forum.emclient.com/t/new-mail-icon-in-tray/62373
@Gary post from the above thread.
There are two ways to show new mail notification; Windows Action Center and eM Client’s own notifications.
You can change the settings in eM Client via “Menu > Settings > General > Notifications”.
If you tick Use system notifications , they will be passed on to the Windows Action Center, and you can configure that in your Windows 10 / 11 settings.
If you untick that, you will get the traditional new mail icon. You may also have to change your Windows Taskbar settings to show the eM Client mail notification.
Note: To show icons in the tray for Windows 10, right click on the empty area in the Taskbar and select “Taskbar settings” and then scroll down to Notification area, and click “Select which icons appear on the taskbar”. Then enable eM Client.
Note: To show icons in the tray for Windows 11,
Right-click on the empty area in Taskbar and select “Taskbar Settings” option. Then click on “Taskbar corner overflow” and enable eM Client on the list.