Configuring preferences and options in Outlook.com
Just getting in on the action here. I'm having the same issue. Samsung Galaxy S10. 26GB space used by Outlook with 2 IMAP accounts. Delete data chips away a little then the phone crashes. I have to hit delete data, then back out of the screen I'm on to avoid a crash. It only deletes a fraction of what it's using so I've had to repeat many times to delete it all.
I'm using BlueMail successfully but thought I'd give Outlook another go as it's cleaner. I'll have to stick with BlueMail for now.