Comcast Corp. says Internet users who download and upload the equivalent of 50 million e-mails a month could lose their Internet access.

Those obsessive Internet customers will first be asked in a warning phone call to dial it back. If that does not happen, Comcast could cancel their service for a year, the company said.

The new policy takes effect Oct. 1.

As part of a Federal Communications Commission investigation and enforcement order, Comcast is separately experimenting with a new real-time Internet-management technology that will slow the online speeds for heavy users during times of Internet congestion.

Comcast posted on its Web site today the new "acceptable use policy." The Philadelphia company also will inform customers through billings, spokesman Charlie Douglas said. He said fewer than 1 percent of the company's 14 million high-speed Internet customers exceed the new limits.

According to the policy, Internet customers whose data flow exceeds 250 gigabytes a month, which is the equivalent of 50 million e-mails or 125 standard-definition movies, would be considered excessive users.

The median data usage for residential Comcast customers is two to three gigabytes a month, the company said in a statement.