It is still unclear what caused an AT&T WorldNet email glitch that left many of the service's 1 million subscribers without incoming email for about four hours today.
Starting at 9 a.m. ET, customers all over the country could send email but not receive messages, AT&T confirmed. The email server is being examined now. In the meantime, service has been reinstated for most.
"By mid-afternoon, 85 percent or more of our customers could receive email without a problem," said Mike Miller, a spokesman for AT&T WorldNet.
"We don't have a clear idea how many customers were affected," he added. "For example, someone could get on one minute, and then five minutes later they couldn't. Also, the problem wasn't focused geographically."
This is the second such "brownout" for WorldNet. Due to a hardware glitch last November, about 50,000 customers were unable to receive email for half a day. In July, the service suffered the opposite problem--a spammer clogged WorldNet customers' outbound email for a few days before being shut down.
WorldNet is not the only major Net access provider to be hit with email problems recently.
Just one day after America Online reached its 10 million member mark in November, the online service suffered a brief, system-wide email outage. And earlier this month, Microsoft Network members using the latest version of the service couldn't send email to AOL subscribers for about nine days.