Hi @Wjbertrand! At this time email changes are best done with our support team. Check out our Community post about email changes for more information on this. For Shared User invitations, those should work as long as a proper email address is entered and that address is associated with a Ring account. The person you are adding will have the option to accept the invitation.
If you are still receiving this error when adding shared users, try removing and reinstalling the Ring app on your mobile device. To reach our support team, please give us a call at one of the numbers available here. We’re taking additional steps to protect our team and help reduce the spread of COVID-19, so this has resulted in longer than normal wait times. If you are outside of the US, please read our response to COVID-19 here to see how to contact support.