outlook mail not syncing deleted messages

I use Outlook mail on both my MacBook Air and my iPhone 8. Recently it started keeping all my mail on the phone even when I delete and empty trash on my Air. I have tried all different settings that I could find and even deleted the Outlook App on my phone and set it up in mail. Still nothing is working. I have to manually delete everything on my phone. I am guessing it is what is clogging up my iCloud storage too. Help! Willing to try most anything.