As reported earlier, some Hotmail users encountered a bug that caused their outgoing e-mail messages to be sent several times. In cases where the multiple e-mails were sent to automated mailing lists, the messages were distributed to dozens or hundreds of users, further increasing Internet traffic.

Hotmail reported Monday that it now has more than 30 million users.

The company said the problem resulted from a routine system adjustment Wednesday evening and was discovered around 10 a.m. PT Thursday. The problem was fixed by 12:30 p.m. PT, Hotmail said.

"It's really unclear how many messages were affected," said Laura Norman, a product manager with Hotmail. "It wasn't pervasive, and it did not happen to every message or to every member."

Lots of mail

Some users reported receiving five to seven copies of messages from Hotmail members.

Internet service providers can have a tough time with such traffic increases, which can clog Internet gateways and delay other e-mail messages.

The problem underscores the increasing visibility and influence of single companies on the Internet. A minor bug in software from Hotmail or America Online Inc. (NYSE:AOL), two of the biggest generators of e-mail, can mean delays or congestion across the online world.