Feedback

Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

History

Self-regulating mechanisms have existed since antiquity, and the idea of feedback had started to enter economic theory in Britain by the eighteenth century, but it wasn't at that time recognized as a universal abstraction and so didn't have a name.

The verb phrase "to feed back", in the sense of returning to an earlier position in a mechanical process, was in use in the US by the 1860s, and in 1909, Nobel laureate Karl Ferdinand Braun used the term "feed-back" as a noun to refer to (undesired) coupling between components of an electronic circuit.

By the end of 1912, researchers using early electronic amplifiers (audions) had discovered that deliberately coupling part of the output signal back to the input circuit would boost the amplification (through regeneration), but would also cause the audion to howl or sing. This action of feeding back of the signal from output to input gave rise to the use of the term "feedback" as a distinct word by 1920.

Feedback loop (email)

A feedback loop (FBL), sometimes called a complaint feedback loop, is an inter-organizational form of feedback by which a Mailbox Provider (MP) forwards the complaints originating from their users to the sender's organizations. MPs 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 MP from which they want to collect users' complaints.

Feedback loops are one of the ways for reporting spam. Whether and how to provide an FBL is a choice of the MP. End users should report abuse at their mailbox provider's reporting hub, so as to also help filtering. As an alternative, competent users may send abuse complaints directly, acting as mailbox providers themselves.

Rationale

Marketers striving for their mail to be delivered have a twofold advantage: they can remove subscribers that don't want to receive that kind of advertising (listwashing), and they can analyze the complaint rate and hence how their advertising meets market expectations. By unsubscribing users who complain, marketers reduce their overall complaint rate per IP or domain, ensuring that targeted mail is much more likely to reach subscribers who actually want to receive it.