Microsoft offers the new Outlook for Windows as a replacement for the mail and calendar apps in Windows 10/11.
This is not an email client in the traditional sense. Rather, it is a WebView container that displays email in a separate window. It uses the mail server’s website to interact with the user interface.
While Outlook for Windows works entirely on the server side (with the exception of HTML/CSS rendering), MAPI is a client-side technology. Therefore, the MAPI protocol cannot be used with Outlook for Windows to send email. Classic Outlook must still be used for this.
Outlook for Windows can only use the SMTP protocol or Microsoft Graph to send email.