On Thursday afternoon, Comcast posted a notice on its e-mail page, apologizing for the loss of service.
"We are currently in the process of upgrading Webmail," the notice read. "We apologize for the inconvenience. Our customer service representatives have no additional information at this time. Please try back later."
Subscribers began posting complaints on Comcast's message boards and on other online forums, such as Broadbandreports.com. In their messages, people said they had no access to their accounts. The complaints related to Comcast systems from Philadelphia, where the company is headquartered, to California.
Perhaps not coincidentally, Comcast on Thursday also launched a redesign of its Web mail service, which lets members read their e-mail through a separate Web site, in much the same way that America Online users can read their messages from the Web.
The updated mail service will feature cosmetic changes to the interface and "improved navigation," according to a notice that Comcast sent to its subscribers.
A Comcast representative was not immediately available for comment.