accessing a wi and send an email, then it is possible to know who sent the email
Users of a Wii can send email via the messaging functions of the Wii. This requires registering the Wii. So it will show you the profile of the sender if they send it to your email address. But, as mentioned in the instructions for this:
Please note: You must have a broadband internet connection, and register your Wii Friend in the Address Book.
It's not foolproof. Anyone with physical access to the Wii could have sent that email. But I don't see how the address could be spoofed.
NOTE: I deleted your other post, since it asked exactly the same question. That is frowned upon here. Asking multiple times does not get you a faster response.