How do FBLs notify senders of complaints?

FBLs deliver complaint notifications via email to the address you registered during enrollment. The messages use ARF (Abuse Reporting Format), a standard structure that automated systems can parse.

Each complaint generates a separate notification (for standard FBLs) or appears in periodic batch reports (for aggregate FBLs). The notifications arrive near-real-time for most providers.

ESPs typically automate FBL processing. Their systems receive the ARF messages, extract recipient addresses, and automatically add them to suppression lists. Manual processing is possible but impractical at scale.

FBL notifications are official complaint letters delivered to your registered office. Sophisticated operations have staff (or automation) that opens each letter, processes the complaint, and updates records immediately.