All messages sent to SBCGLOBAL customers apparently have been blocked by SBCGLOBAL's mail servers.
I reported the problem to the SBCGLOBAL postmaster. I didn't hear back from the postmaster so I became suspicious. It turns out that there was a reply back to me within a few hours but it had been blocked by MY spam filters!
I found their message in MY spam folder.
It is a difficult and frustrating world that we live in. (sigh)