You can easily access the email addresses of all the members of a circle or the whole organization.
Circle Member List
Navigate to a circle page, then the Members tab.
Click the envelope icon button and choose from one of the options available.
You can copy email of:
all circle members
all core circle members
all members in core roles in the circle
Organization Member List
Admins can access the list of all users email addresses.
Go to Administration from your avatar
Go to Manage users
From here, you can Export file by clicking on the icon at the right side of the screen. This will generate an export with all users in the organization
Filter the list of users directly in the file to copy the email addresses in your clipboard.
Roles Templates Member List
Admins can access the list of all members assigned to Roles Templates in the organization.
For that, go to the Administration menu:
Go to Role templates
Click on the 3 dots at the very right side of the template
Select Export members. You'll get a list of users who fill role templates including their contact details.