If you want to change the email address of a person from Voice, follow the steps below:
While logged into V3, select Voice view (telephone icon, gold circle in image below) and then select whichever category the person's message is under. In our example, we selected All Messages (light blue box in image below), so we can see everyone.
Select the number with the email you want to change (light blue box in image below).
The profile of the person would be displayed on the right hand of the screen
Hovering over the email field would make the Edit option appear. Click on it.
Edit the email of the person, and then click on Save.
The email would be updated to the new address on the profile of the person (yellow box in image below).