"AOL was caught red-handed censoring e-mail, and now the public knows their credibility is gone," said Adam Green, a spokesman for MoveOn.org Civic Action, in a statement.

The protests began after AOL announced plans to charge fees to e-mail senders, such as marketing companies, that want to ensure their mails are pre-accepted by recipients. The program, which was announced by AOL and Yahoo Inc. in October, will use technology from Goodmail Systems Inc. in Mountain Valley, Calif., to differentiate e-mail sent by groups or companies that want to assure AOL customers of its authenticity (See "Fee-based e-mail delivery plan raises eyebrows"). The system would affect only e-mail sent to AOL's approximately 18 million customers.