Found under Client Config > Business: General > Is Email Required? (Yes/No, default No; only visible when account members are enabled):

• No — when a manager adds a member, the form asks only for First Name, Last Name and optional Phone. The system creates the member account with an internal placeholder address, so the member cannot log in or receive emails on their own; the manager does everything for them.
• Yes — the member form also shows a required Email field. The member account is created with that email (it must not already be in use), and the New Created User email with their login details is sent to it so the member can log in themselves.

Changing the setting affects members added afterwards; existing members keep whatever email they have.