America Online is vowing to carry out its plans to institute fees for mass senders of e-mail, despite protests from groups representing 15 million people that claim the move will stifle communications instead of merely halting spam.

Political group MoveOn.org Civic Action, the AFL-CIO labor union and other organizations have criticized the service, which will charge senders a fee to route their messages directly to AOL users’ mailboxes without first passing through AOL junk mail filters.