Feedback loop (email)

MPs can receive users' complaints by placing report spam buttons on their webmail pages, or in their email client, or via help desks.

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.

[4] As sketched above, the process implies that Spencer, besides being the author (or sender) of the message, is connected to the postmaster responsible for his mail domain.

RFC 6650 addresses the latter shortcoming by proposing auto-subscribe just-in-time FBLs, which can be started by sending an unsolicited abuse report with further directives (at a minimum, a way to unsubscribe).

SendGrid reports that the Gmail FBL, developed and launched by Julian Tempelsman and Sri Somanchi, is effective at identifying spam that other anti-spam systems miss.

A sender and a recipient connected by a mailbox provider (MP). The feedback provider and the feedback consumer are the two formal endpoints of the feedback loop (blue arrow). Senders need to subscribe, possibly using a web form similar to the one depicted on the upper left corner, in order to become feedback consumers. Recipients typically click a spam button on a web mail page to start the process.