Using shared content results in an email being sent to your specified recipient. Kind of the point, right?
The email is always sent from email@example.com, and the reply-to email address is the email address you used to log into your account - so if your recipient replies to the message, it will come to you.
If the recipient email address you specify isn't correct, you will receive an email notifying you of the failed sharing attempt and you can try again!
The email that your recipient gets looks a little like below:
Admins can change the default "Showcase Workshop" header image using the Email Settings.