What do "Identifiers Flagged" mean in Google Postmaster Tools Feedback Loop?

Key findings

• Purpose: Identifiers Flagged aim to help senders pinpoint specific campaigns, client segments, or email batches that are attracting a high volume of spam complaints from Gmail users. They provide granular data beyond just a general spam rate.
• Source of identifiers: Typically, these identifiers are extracted from the Feedback-ID header that senders include in their email. This header is designed for feedback loops and can contain multiple unique values representing aspects like account ID, campaign ID, or batch ID.
• Google's selection logic: Google's system intelligently selects identifiers it deems unique and relevant. It may even infer identifiers from other consistent elements within the email if a formal Feedback-ID header isn't present or specific enough.
• Data aggregation: The number shown for "Identifiers Flagged" represents the count of unique identifiers that triggered a feedback loop complaint for a given period.
• Thresholds: Google applies volume thresholds to prevent identifiable information from being reverse-engineered from low-volume data. This means that if complaint volumes are too low for a particular identifier, it might not be displayed.

Key considerations

• Consistency is key: For accurate reporting, ensure consistent sender identifiers across all sends from your platform. This helps Google reliably group complaints.
• Investigate discrepancies: If the flagged identifiers don't match your expectations based on your Feedback-ID header, it could indicate either insufficient volume or that Google is identifying other consistent elements within your email stream. Further details on how the Gmail Feedback Loop works are available in our guide on how Gmail's Feedback Loop (FBL) works.
• Volume sensitivity: Smaller senders or campaigns with very low complaint rates might not see specific identifiers flagged, even if they have configured their Feedback-ID headers correctly. This behavior is detailed in guides like Amazon Web Services' Understanding Google Postmaster Tools which explains how spam complaint data is presented.
• Holistic view: Always view "Identifiers Flagged" in conjunction with other Postmaster Tools data, such as spam rate and domain reputation, for a complete picture of your email program's performance. For a broader perspective, consult our Ultimate Guide to Google Postmaster Tools V2.

Key opinions

• Expected source: Marketers generally believe that the "Identifiers Flagged" should directly correspond to the values defined within their Feedback-ID header, such as account, campaign, or batch IDs.
• Discrepancy observations: Some marketers report that the numbers or specific identifiers displayed in Postmaster Tools do not always perfectly align with the data they expected based on their Feedback-ID configurations.
• Importance of uniqueness: There's a consensus that the identifiers defined in the Feedback-ID header need to be unique and consistent for Google to reliably report on them. Without unique identifiers, troubleshooting can become difficult, as discussed in our article on why your emails fail.
• Volume considerations: Marketers recognize that low sending volumes might result in Google not showing specific identifiers due to privacy thresholds, even if complaints exist.

Key considerations

• Verify Feedback-ID setup: Regularly check that the Feedback-ID header is correctly implemented and contains the intended unique identifiers for tracking campaigns. This is a fundamental step in monitoring email deliverability.
• Understand Google's limitations: Be aware that Google prioritizes user privacy and will not disclose identifiers if the volume is too low to prevent reverse-engineering of user data. This is part of the broader guidelines for email senders.
• Correlation with spam rates: Always analyze flagged identifiers in conjunction with the associated spam rates to understand the true impact. A high number of flagged identifiers with a low spam rate might be less concerning than a few identifiers with an extremely high spam rate.
• Continuous monitoring: Implement ongoing monitoring of your Google Postmaster Tools data to quickly identify and address any emerging issues with flagged identifiers. Insights from Beehiiv's guide on Google Postmaster Tools can further assist in successful setup and utilization.
• Impact on domain reputation: Addressing issues highlighted by flagged identifiers is crucial for maintaining a good domain reputation with Gmail. Learn more about improving your reputation in our guide to improving domain reputation using Google Postmaster Tools.

Key opinions

• Privacy over granularity: Experts confirm that Gmail will only show an ID for a header if the complaint volume is significant enough to prevent senders from reverse-engineering individual user complaints, ensuring privacy.
• Consistent sender ID expectation: There's an expectation that a consistent sender ID should be present across all emails originating from a platform for Google to accurately track and report. This aids in better spam management, a key aspect of managing spam traps.
• Google's inferred identifiers: Even if a specific Feedback-ID isn't present, Google can identify common, consistent elements within emails that draw complaints and use those as de facto "FBL identifiers" in the reporting.
• Beyond the header: Experts clarify that "things" Google picks for flagging aren't limited to the Feedback-ID header itself. Any consistent element in the email that allows Google to group complaints might be used. This flexibility is also seen in how abuse rates are sometimes reported even without sends.

Key considerations

• Strategic Feedback-ID design: Senders should design their Feedback-ID headers to contain a hierarchy of unique identifiers (e.g., client ID, campaign ID, list ID). This allows for both broad and granular analysis of complaints, provided volume thresholds are met.
• Understanding Google's adaptive nature: Deliverability experts advise that Google's system is adaptive. If explicit Feedback-ID values aren't providing useful insights, examine other consistent elements within your email creative or sending patterns for potential complaint sources. This aligns with broader deliverability strategies found on sites like Spam Resource.
• Interpreting missing data: A lack of flagged identifiers doesn't necessarily mean zero complaints, but rather that the volume is too low for Google to report specific identifiers. This is a common scenario when Postmaster Tools data is missing.

Key findings

• Data aggregation: The Postmaster Tools Feedback Loop dashboard aggregates data on spam complaints, showing the average spam rate and the number of unique identifiers that triggered these complaints.
• Privacy thresholds: Google's documentation highlights that data, including flagged identifiers, is only displayed if there's enough volume to prevent individual user identification, ensuring privacy protection.
• Utilizing Feedback-ID header: Senders are encouraged to implement the Feedback-ID header in their outgoing emails to provide Google with structured identifiers for reporting.
• Actionable insights: The flagged identifiers are intended to help senders isolate problematic traffic streams, allowing them to take targeted action to reduce spam complaints and improve their sending reputation.

Key considerations

• Accurate header implementation: Ensure your Feedback-ID header conforms to the specified format and contains values that are genuinely unique to your internal campaigns or client segments.
• Correlation with other metrics: Documentation emphasizes that Feedback Loop data should be reviewed alongside other metrics in Postmaster Tools, such as IP reputation and domain reputation, for a comprehensive understanding.
• Responding to complaints: Even if specific identifiers aren't always shown, a high overall spam rate still signals a need for list hygiene and content optimization to reduce complaints. Documentation also covers the broader aspects of signing up for the Gmail FBL and interpreting its data.