The Wishlist Sharing on Smart Wishlist is currently handled using a 3rd party service known as Addthis.
Here, the “from” is an editable field and is not set to anything by default. It is upto the sender to specify the “from” email address.
If you want, we can set the default “from” email address to anything you want. But it would still be editable and the users would have the option to change it.
Add the below code towards the closing </body> tag in layout/theme.liquid. Make sure to replace email@example.com with appropriate email id.