My Outlook 2016 is locking up -- and it has become so frequent that I've had to keep the Windows 10 Task Manager running all the time so I can have a quick way to terminate & restart Outlook to make it useful.

I suspect the problem is caused by Outlook on my Windows 10 desktop syncing with the default mail app on my iPhone. I don't recall ever setting up either app to sync with the other, but it's doing that. And the problem appears most likely to happen when I'm on the desktop and I attempt to move a message from the Inbox to one of my Outlook folders.

I don't want syncing. I don't like syncing. But I do like for both the desktop and the iPhone to get a copy of all incoming email.

So, how can I fix this?