Tab: Business > General. Only shown if you have the Account Members module or are on the Base/Pro/Enterprise plan. Options: Yes / No (default No). Global only.

This applies to subscription account members — the extra people a subscriber can add to their account (the Subscription Members feature). When Yes, the email field becomes mandatory when a member is added or edited and the form shows the error User's Email is Required if it is blank. When No, members can be created with just a name.