Removing Mail app Documents & Data

I found a workaround to the issue reported below.

“Hello,

I'm trying to free up storage on my iPhone. I've removed all email accounts from my phone and deleted the Mail app, but looking at my iPhone storage, it still says that the documents & data for the app is taking 691.9 MB of my storage. It acts like the app is offloaded and even shows the offloaded icon next to the name on my iPhone storage page, no matter how many times I click "Delete App" it doesn't go away. None of the mail is saved to my iCloud. It's just the remaining storage that refuses to go away. What can I do to fix this and free up the storage?”

My device is an older iPad Pro 2nd Gen. I did everything the person did but ensured iCloud Mail was Off then Deleted the Mail app and if visible in on the device Storage then Reinstalled the Mail app, checked the Mail app storage reduction in Storage then repeated the process until the Mail app disappeared completely from Storage. I repeated the cycle 8 times to clear 16gb of Mail app documents and data.

It was tedious but freed the superfluous data accrued in the iOS Mail app and recovered storage.