When you restrict email notifications, enterprise members can only use an email address in a verified or approved domain to receive email notifications about activity in organizations owned by your enterprise account.
Note: Domain approval is currently in beta and subject to change.
The domains can be inherited from the enterprise account or configured for the specific organization. For more information, see "Verifying or approving a domain for your enterprise account" and "Restricting email notifications for your organization."
After you enable email restrictions, members can receive email notifications at verified email addresses within domains that you've verified or approved. For more information, see "Verifying your email address."
If email restrictions are enabled for an enterprise account, organization owners cannot disable email restrictions for any organization owned by the enterprise account. If changes occur that result in an organization having no verified or approved domains, either inherited from an enterprise account that owns the organization or for the specific organization, email restrictions will be disabled for the organization.
Before you can restrict email notifications for your enterprise account, you must verify or approve at least one domain for the enterprise account. For more information, see "Verifying or approving a domain for your enterprise account."
In the top-right corner of GitHub, click your profile photo, then click Your enterprises.
In the list of enterprises, click the enterprise you want to view.
In the enterprise account sidebar, click Settings.
Under "Settings", click Verified & approved domains.
Under "Enforcement preferences", select Restrict email notifications to domain email.