How does Validity modify ARF reports, and what impact does it have on identifying recipients for list removal?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 May 2025
Updated 18 Aug 2025
8 min read
As an email sender, managing your recipient lists is crucial for maintaining good deliverability and avoiding spam complaints. One of the primary mechanisms for receiving feedback about unwanted mail is through Abuse Reporting Format (ARF) reports, also known as feedback loop (FBL) reports. These reports are essentially complaints from recipients forwarded by Internet Service Providers (ISPs) and mailbox providers (MBPs).
Validity, a major player in email deliverability, processes a significant volume of these ARF reports, especially since their acquisition of other services. This naturally leads to questions about how they handle these reports and what implications their processing has for senders attempting to identify specific recipients for list removal. Let's delve into the specifics of how Validity operates with ARF reports and its impact on your list hygiene.
The fundamentals of ARF reports
ARF reports, as defined by RFC 5965, provide a standardized way for MBPs to report feedback about received email to the sender. This feedback typically indicates that a recipient marked an email as spam, but it can also include other types of abuse. The core purpose is to give senders actionable data to suppress (unsubscribe) users who no longer wish to receive their mail, thus preventing further complaints.
Many major mailbox providers, including Yahoo, offer FBLs as part of their postmaster tools, which are usually triggered when emails matching a specific DKIM domain are marked as spam. These reports are critical for senders to maintain a healthy sending reputation and avoid being placed on email blocklists (or blacklists). Google and Yahoo provide valuable spam complaint data through their respective feedback loops.
Validity acts as a central aggregator and processor for many of these feedback loops. By enrolling with Validity's Universal Feedback Loop (UFL), senders can receive consolidated complaint data from various participating mailbox providers. This streamlines the process, as individual FBL registrations with each provider can be cumbersome.
The efficiency of this system largely depends on the sender's ability to quickly identify and remove complaining users from their mailing lists. Neglecting to process these reports can lead to higher complaint rates, which will negatively impact your sender reputation and cause your emails to land in the spam folder, or even result in your domains or IPs being placed on an email blocklist.
How Validity processes ARF reports
While the standard ARF format encapsulates the original email as an attachment, allowing for full review, Validity's processing involves a crucial modification: the redaction of personally identifiable information (P.I.I.). This means the actual email address of the complaining recipient is not directly provided in the ARF reports you receive via Validity. This measure is primarily for privacy protection.
The question often arises whether it's Validity or the individual ISP that performs this obfuscation. In reality, some mailbox providers might redact P.I.I. themselves before sending the reports to Validity. However, Validity ensures that for all reports it distributes through its UFL, the recipient email address is redacted. This is a consistent policy to comply with privacy regulations and to streamline data delivery while maintaining user anonymity.
This redaction doesn't render the reports useless. Instead, senders are expected to use unique identifiers that they embed within their emails to pinpoint the complaining recipient. These identifiers allow you to match the complaint back to a specific subscriber record in your database without needing their explicit email address in the report itself.
This approach is a necessary balance between providing useful feedback to senders and protecting the privacy of individual recipients who report spam. It shifts the responsibility of recipient identification from the feedback loop provider to the sender, who holds the key to mapping unique identifiers back to their subscriber database.
Understanding P.I.I. redaction
When you receive an ARF report through Validity's Universal Feedback Loop (UFL), you will notice that sensitive personal information, such as the exact recipient email address, is removed or anonymized. This is a deliberate measure to protect user privacy. Instead, the reports contain other data points that, when correlated with your internal records, allow you to identify the specific subscriber who complained.
Identifying subscribers for suppression
The primary impact of Validity's (or the MBP's) P.I.I. redaction is that you cannot directly pull an email address from the ARF report for list suppression. This necessitates a strategic shift in how senders approach email list management and feedback loop processing. You need to implement a system that allows you to uniquely identify each email sent.
This typically involves embedding unique identifiers in your emails. Common methods include:
Custom headers: Adding a unique, non-visible header to each email (e.g., X-Campaign-ID or X-User-ID) that contains a hash or an internal identifier for the recipient or campaign. When the ARF report comes back, this header is often preserved and allows for identification.
Unique Message-IDs: The Message-ID header is typically unique to each email sent and is usually included in the ARF report. You can use this to link back to your sending logs and identify the specific recipient.
This method ensures that privacy is maintained while providing senders with the necessary data to perform crucial list removals. Without this internal correlation, processing ARF reports from Validity or other FBLs with P.I.I. redaction would be challenging for effective list hygiene.
Traditional ARF reports
Content: Includes the full, original email as an attachment, including the recipient's explicit email address.
Identification: Direct identification of the complaining recipient via their email address in the report.
Privacy: Less emphasis on P.I.I. protection within the report structure, relying on sender's responsible handling.
Validity's ARF reports
Content: Redacted P.I.I., specifically the recipient email address, while retaining other metadata and the original email body.
Identification: Requires senders to use unique, encoded identifiers in their emails to match complaints to subscribers.
Privacy: Enhanced privacy protection by omitting direct P.I.I., aligning with data protection standards.
Optimizing for ARF report processing
To effectively use ARF reports from Validity for list removal, you need a robust system in place. The first step is to ensure that every email you send carries a unique identifier that links back to the specific recipient in your database. This could be a unique customer ID, a campaign ID combined with a subscriber hash, or even a unique Message-ID that you log.
When you receive an ARF report, your system should parse the report to extract this unique identifier. Once extracted, you can then use this identifier to look up the corresponding subscriber in your database and suppress (or unsubscribe) them. This automation is vital for timely list hygiene, as delays can lead to more complaints and damage your sender reputation.
Setting up unique identifiers for FBLs
To effectively process FBLs for list removal, you must embed unique identifiers within your emails. These identifiers (e.g., a X-Feedback-ID or List-Unsubscribe header) allow you to link a complaint back to a specific subscriber in your database, even without their explicit email address in the ARF report. Ensure your email platform supports custom headers or unique Message-IDs that can be logged and correlated.
Automating your FBL processing and list suppression is a critical best practice. Manual processing is prone to errors and delays, which can quickly lead to an increase in spam complaints and a decline in your sender reputation. Many email service providers (ESPs) offer built-in FBL processing, or you can develop custom scripts to automate the workflow.
Regularly monitoring your domain and IP reputation, alongside efficient FBL processing, ensures your emails reach the inbox. Being proactive in removing unengaged or complaining recipients protects your sender score and prevents your domain from appearing on a blacklist or blocklist.
Ensuring effective list hygiene
Validity's role in processing ARF reports is integral to the email ecosystem, particularly for senders who rely on comprehensive feedback loops. While the redaction of recipient P.I.I. is a notable modification, it doesn't diminish the utility of these reports for list removal. Instead, it places a greater emphasis on senders to implement robust internal tracking mechanisms.
By understanding this processing and adopting best practices for embedding unique identifiers and automating list suppression, you can effectively leverage ARF reports to maintain a healthy and engaged subscriber list. This proactive approach is key to improving your email deliverability and protecting your sender reputation in the long run.
Views from the trenches
Best practices
Always embed unique identifiers in your email headers or body for easy lookup.
Automate the processing of feedback loop data to ensure timely list removals.
Regularly monitor your complaint rates across all mailbox providers.
Segment your audience to reduce the likelihood of irrelevant emails causing complaints.
Common pitfalls
Failing to embed unique identifiers, making it impossible to identify complainants.
Manually processing ARF reports, leading to delays and increased complaints.
Ignoring feedback loop data, which significantly harms sender reputation.
Assuming all ARF reports will contain explicit recipient email addresses.
Expert tips
Leverage the Message-ID header for correlation with your sending logs if custom headers aren't feasible.
Consider how DMARC aggregate reports can complement FBL data for broader insights.
Regularly audit your list suppression process to catch any inefficiencies.
Implement double opt-in to reduce initial spam complaints and improve engagement.
Marketer view
Marketer from Email Geeks says: The post makes it sound like Validity is actively modifying the ARF reports before forwarding them on, and I'm curious if this is actually the case. I thought ARF was supposed to wrap the original email as an attachment and send it on.
2023-09-27 - Email Geeks
Marketer view
Marketer from Email Geeks says: I agree, perhaps the post has it partly wrong or assumes more obfuscation than what truly occurs. I've always thought the ISPs were primarily responsible for any redaction.
Content: Redacted P.I.I., specifically the recipient email address, while retaining other metadata and the original email body.
