The above solution worked perfectly for me.
Wordpress 4.8
Jetpack 5.1
In the WP Admin view:
I’d like to paste a screenshot here, but I can’t, but what you would have seen is the screen visible when Settings/Sharing is selected. Some sharing buttons are unused in “Available Services”, some contained in “Enabled Services”, with a few to the right that are behind the “More” button in the “Live Preview”. In all of this, there is no button for email. I know it should be there, but it is not.
I’m running 4.8 (I think) and I’m not seeing the email sharing button. It says I’m up to date, so I’m not sure where 5.1 is coming from.