iphone backup restores my work email

We recently realized that when restoring a new iPhone from iCloud backup, our internal Exchange email from work is restored and working without entering any credentials on the new iPhone. We need to find out exactly what is backed up to iCloud, credentials or emails or both? What is to prevent someone who somehow gains access to my icloud credentials from restoring a rogue iphone and gaining access to my corporate email and other corporate data? Does my corporate data then reside on an iCloud server? If so is it encrypted? Thank you to whoever can shed some light on this topic.