"We're working to fix it," said Hotmail product manager Laura Norman. "We're beginning to bring it back online right now and will have it fully restored in next couple of hours."
One Hotmail user reported hours-long delays in receiving email through her account, but Norman said the server outage did not affect mail delivery, only account access.
With 30 million registered users, Hotmail leads the pack of Web-based email providers. That extraordinary volume also means technical problems can wind up affecting hundreds of thousands, or even millions, of email exchanges.