Do not display New Mail alert for users
Supported on: At least Windows Server 2008 R2 or Windows 7
Registry
HKCU
software\policies\microsoft\office\16.0\outlook\preferences Value name: newmaildesktopalerts
Enabled: newmaildesktopalerts = 0
Disabled: newmaildesktopalerts = 1
Description
By default, users receive an alert message on their desktops when new mail arrives. By enabling this setting, the alert is not displayed for new mail.