How much can an IT department see if I sign in to my company Outlook/Teams account on an old iPhone?

I use Outlook and Onedrive on my personal phone and whenever I sign in to my company account, it tries to “take over” the entire app and I’m worried they can see all my emails and Onedrive files.

I have an old iPhone 7 on like iOS 12 that I can use though. I’ve deleted everything personal on that phone a long time ago, but are they able to finangle their way into all the files that used to be …

account department iphone old outlook privacy sign teams