Do FBL messages get generated from bulk folders and how does this affect understanding email deliverability metrics?

While some in the deliverability community previously believed Feedback Loop (FBL) messages could not originate from emails sent to bulk or spam folders, a broader consensus, including documentation from major Internet Service Providers, clarifies that FBLs are indeed triggered by a recipient's action of marking an email as spam, regardless of its initial folder placement. However, emails that land directly in bulk folders are considerably less likely to be seen by recipients, which significantly reduces the probability of a user reporting them. Consequently, a low FBL rate often does not accurately reflect true inbox placement, as a substantial volume of emails may be silently routed to spam folders without generating any user complaints. This distinction is crucial for understanding email deliverability metrics, as relying solely on FBLs can lead to a misleadingly optimistic view of sender reputation and inbox performance.

While Feedback Loop (FBL) messages are user-initiated reports that can technically arise from emails in bulk folders, their generation is significantly less probable in such scenarios. This creates a critical challenge for understanding deliverability: a low FBL rate may falsely signal excellent inbox placement, as substantial volumes of email could be silently routed to spam folders without ever being seen, let alone reported, by recipients. Consequently, FBLs primarily indicate active user rejection rather than a comprehensive measure of inbox success, highlighting the necessity for a broader analytical approach to deliverability metrics.

Feedback Loop (FBL) messages are indeed generated when users mark an email as spam, irrespective of whether it landed in their inbox or a bulk/junk folder. This means FBLs provide a comprehensive signal of user dissatisfaction across all email placements, making their understanding vital for accurate deliverability metrics. While it is true that emails silently filtered into bulk folders are less likely to be seen and thus reported, any complaints originating from these folders still significantly impact sender reputation, alerting Internet Service Providers (ISPs) to unwanted mail and potentially leading to more aggressive filtering. Therefore, a low FBL rate can still mask underlying deliverability issues if a large volume of mail is being shunted to spam unseen.

Despite emails frequently landing in bulk folders, Feedback Loop (FBL) messages can still be generated from them when a recipient actively marks a message as spam. This consistent explanation from major email providers, including Google, Microsoft, and Amazon, underscores that FBLs are a direct reflection of user action rather than initial folder placement. While an email routed to a bulk folder is less likely to be seen and thus less likely to generate an FBL, any complaint still negatively impacts sender reputation. Consequently, a low FBL rate should not be the sole indicator of strong deliverability, as it may obscure significant volumes of mail that are silently shunted to spam without ever being reported.