Hi,
The email button was removed as it didn't serve any purpose thus far. The button was added in old versions of HikaShop but was never working.
It's actually in our plans to add it again in the future.
The goal of the button would be to allow you to enter email addresses with a message in a form you'd see upon clicking on it and it would send an email to all the email addresses.
But you don't really need that. You can just open your email client, get the sharing link you see when you select "email" in the "share" dropdown, and add it to an email you would send to your friends.