Most likely, but that isn't an excuse and it an incredibly stupid way to build an email client.
MAYBE give the option if for some reason I want to do it. But for it to be the default is a stupid idea. You cannot convince me there is a valid reason for this to be a thing.
It's like that because mobile clients need cooperation from the server to have push notifications, and you can't have IMAP servers cooperate in that regard :-) so the outlook servers fetch the mail for you and then send you the notifications.
I wouldn't have microsoft read my email either, of course. Thankfully in windows you have dozens of clients to choose from.
You can't realiably poll from a mobile phone. Your app may not be allowed to execute any code, let alone make a network request for hours, or maybe forever.
