While logged into V3, select Groups view (people icon, gold circle in image below) and the name of the group. We chose Named in our example (brown box in image below).
Select the group that the person belongs to.
Information about individuals in the group would be displayed in the right-hand side of your screen.
Select the person whose email you want to change. We selected Freddie Mercury (gold box in image below).
Information about the person, including the email (brown box in image below) would be displayed on the right-hand side of your screen.
Hover around the email and the option to Edit would appear (see image below). Click on it.
Input the new email address, and then click Save (see image below).