Only if you want Push. Pull / Fetch is initiated from the device. But the Push is initiated from a server. So the server must get a notification of a new email

Only if you want Push. Pull / Fetch is initiated from the device. But the Push is initiated from a server. So the server must get a notification of a new email. IMAP-PUSH / Outlook has support for that on a desktop, but not on a mobile device. So if you get push from a 3rd party email, they listen for new emails in your name. Whether via the technologies mentioned above, or some other APIs, it's done on a server, and the server triggers the Push to your phone.