[Favorites] How do I manage Favorites?
Press the "Favorites" button next to the sender if you receive an email you are interested in.
Once the sender is designated as a Favorite, you can see a collection of emails from your Favorites. You can also get alerted when you receive emails from your Favorites by applying alert settings.

You can also remove that sender from your Favorites by pressing the "Favorites" button again or go to Settings > Favorites to delete the sender from your Favorites.