There is an event on the Outlook connector named NewMail. If you click on the little arrow in the upper right corner of the event, you can expand it and see the Mail property. If you extract a proxy, then you can access this Mail object's properties, methods and events. From here, you can do whatever you need to it without polling. Be aware though, that this event fires before the mail is visible in Outlook to the user. In my screenshot, you can see I am checking the subject of a new mail when it arrives and marking it as Read if it matches a specific subject.
I believe so. I only mentioned it because if you planned to move the email or do something that took a long time, it might delay the user being able to know that the email arrived and do anything to it themselves.
When Multiple Accounts are configured in Outlook Mailbox ,Automation will run only on the default account, one thing we have to make sure is to setup the desired account as Default in outlook itself(on which automation needs to be performed).In outlook go to File->Account Settings ->Select the desired Email address or Account out of Shown Accounts -> Select option Set as Default in above pane.