Residual microsoft data on my iphone?

I'm trying to scan some important documents using my iPhone 11. The built in scanner (in e.g. Notes) doesn't seem to allow me to use a wide view so I'm having to resort to Microsoft Lens.

Being the paranoid person that I am; I downloaded Microsoft Lens and went into settings->privacy settings. Here it shows me an old email address.

Somewhere on my iPhone or in my iCloud there is Microsoft data hiding - which I don't like. I've removed all the Microsoft apps from backups on all my devices, and uninstalled & reinstalled Microsoft Lens using the method described here: https://discussions.apple.com/thread/250190465. But it still knows my email address.

Whereabouts its it getting this information from and how can I delete it?

The account information is most probably stored in the Keychain on the phone.

Unfortunately there's no user interface provided for the Keychain beyond what the individual app developer (such as Microsoft) provided with the app.

This means that if the app does not provide an option to delete the data, your only choice is to erase the whole Keychain (and thus the whole phone). There's no possibility of erasing just a single item in the Keychain.