A feedback loop (FBL), sometimes called a complaint feedback loop, is an inter-organizational form of feedback by which an internet service provider (ISP) forwards the complaints originating from their users to the sender's organizations. ISPs can receive users' complaints by placing report spam buttons on their webmail pages, or in their email client, or via help desks.

The message sender's organization, often an email service provider, has to come to an agreement with each ISP from which they want to collect users' complaints, or sends them to addresses where such feedback might be received.