The nonprofit DearAOL.com Coalition was formed in February to protest what it called AOL's creation of an e-mail tax that would harm the free and open use of the Internet (See "Critics rip AOL's pay-to-send e-mail system").

In an e-mail message Thursday, organizers of the group said their fears of AOL trying to control e-mail were confirmed when e-mails they sent to AOL users were blocked from being delivered.

The problem was found when more than 150 people tried to sign a petition against the certified e-mail proposal and send messages about the efforts to people they know who use AOL. The messages were apparently blocked by AOL's antispam filter, which sent a bounceback message informing them that their e-mail "failed permanently," according to the group.

"This proves the DearAOL.com Coalition's point entirely: Left to their own devices, AOL will always put its own self interest ahead of the public interest in a free and open Internet," said Timothy Karr, campaign director of Free Press, a national, nonpartisan media reform and Internet policy issue group, in a statement. "AOL wants us to believe they won't hurt free e-mail when their pay-to-send system is up and running. But if AOL is willing to censor the flow of information now to silence their critics, how could anyone trust that they will preserve the free and open Internet down the road? Their days of saying 'trust us' are over -- their credibility is gone."

The company, however, says the problem was inadvertent and has been fixed.