Suggested email addresses in Mail App

How can I delete ALL the suggested email address in the Mail App on an iphone? I want them ALL gone, as if the phone were brand new. There are just too many to remove one by one, so how can I just remove them ALL from the app memory? Nothing is saved to the icloud and I even set up a whole new email account, but the suggested email address are saved inside the app...but I want them ALL gone.