You can use SBCGlobal email whenever you need it for Internet services, i.e. to subscribe to a newsletter, create a social media account, subscribe to services, send and receive emails, and much more. Configure the SBCGlobal Email Setting correctly to avoid problems.
https://www.customerservicesforyou.com/email/sbcglobal-net-email-server-settings/
To use the SBCGlobal email service, you must subscribe to one of the AT&T services because the SBC represents a fraction of AT&T. You must also configure the SBCGlobal Mail Setting to use the service.