Apple iCloud silently blocks certain messages without spam filtering. It is not a reliable email forwarding option and should be used with caution.
To setup email forwarding with iCloud, please follow the steps below.
  1. Click the Show Actions menu gear near your iCloud Mail web interface at lower left of screen.
  2. Select Preferences from the menu that has shown.
  3. Open the General tab.
  4. Make sure Forward my email to is checked under Forwarding.
  5. Enter the email address to which you want incoming messages automatically forwarded following Forward my email to.
  6. You also have the option to have emails deleted from the iCloud Mail account once they have been forwarded.
  7. Click Done.