Built for today, designed for the future - The new Outlook for Windows is ready when you are

PeterForster The MAPI API has been around for decades and is very powerful, robust, and available. The API is accessible by nearly all programming & scripting languages on Windows. MAPI is used by numerous first & third party applications to send mail. One example off the top of my head, is "Books of Quick" (Intuit's desktop accounting software). This website forbids me from posting the correct name - wtf Microsoft?

Another example:  it is very easy to use MAPI in PowerShell. Not just for sending email, but monitoring email folders. We use this to run a script that constantly checks a shared folder for new email, parses it and does any/all of the following: display a toast popup for email in shared mailboxes & folders other than Inbox, create calendar meeting requests, create tasks/todo items, forward the email, move the email to different folders/mailboxes, launch applications, and/or send SMS text messages to staff.

"Classic Outlook" rules cannot do all this, and the "New Outlook" rules can do even less.