how to recover my email icon

From support.apple.com

https://support.apple.com/en-us/HT204221

“Restore a built-in app that you removed

1. On your iOS device, go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap  to restore the app.
4. Wait for the app to restore, then open it from your Home screen.“

Download it from the App Store