Can ESP clients sign up for Validity FBL and how do they validate their IPs/domains?
Matthew Whittaker
Co-founder & CTO, Suped
Published 5 May 2025
Updated 19 Aug 2025
9 min read
When delving into email deliverability, one common question that arises is about Feedback Loops (FBLs). Specifically, many wonder if Validity's FBL program, known as the Certified Sender Alliance (CSA) FBL, is exclusively for Email Service Providers (ESPs) or if their individual clients can also enroll. This is a crucial distinction, as FBLs provide valuable data on spam complaints, which is essential for maintaining a healthy sender reputation and achieving good inbox placement.
Understanding who can sign up and how the validation process works for IPs and domains is key to leveraging these services effectively. The process involves demonstrating control over the sending infrastructure, whether it's an IP address or a domain name. This article will clarify the roles of ESPs and their clients in the Validity FBL signup process and explain the common methods of IP and domain validation.
Can ESP clients sign up for Validity FBL?
The short answer is that yes, ESP clients can sign up for Validity FBLs, but there's a nuance to how this typically plays out. While the program is often associated with ESPs because they manage large volumes of email for many clients, individual senders with their own dedicated IPs or domains also have the option to enroll directly. The primary requirement is the ability to validate ownership and control over the sending infrastructure.
For many ESP clients, the Email Service Provider handles the FBL registrations on their behalf. This is often the most practical approach, as ESPs already have established relationships with mailbox providers and are equipped to manage the technical aspects of FBL data reception and processing. If you are using an ESP, it is worth checking with them to see what FBLs they are already enrolled in and how they manage complaint data for your sending. This is a key part of ESPs managing client deliverability responsibilities.
However, if an ESP does not offer this service or if a client prefers direct control, individual signup is an option. The crucial factor is being able to demonstrate that the IPs or domains in question are under your direct control, which brings us to the validation process itself.
IP and domain validation methods
Whether you are an ESP client or an independent sender, validating your IPs and domains is a prerequisite for FBL enrollment. This validation ensures that you are the legitimate sender and have the authority to receive complaint data for the specified sending entities. There are typically two main methods for this: IP address validation and domain validation.
For IP address validation, the most common method is through Reverse DNS (PTR) records. Mailbox providers, including Validity's partners, often require that your sending IPs have valid PTR records that resolve to a proper hostname. Ideally, this hostname should align with a domain used in your DKIM signatures. This provides a layer of verification that the IP is indeed controlled by the stated domain owner. For shared IP pools managed by an ESP, the ESP will typically handle PTR record setup.
The validation process for IPs can involve querying DNS records to confirm the PTR setup. If you are a client using a dedicated IP from your ESP, you would need to coordinate with them to ensure the PTR record is correctly configured to reflect your sending domain or a domain under your control.
Domain validation process
For domain validation, the process usually involves adding specific DNS records to your domain's DNS settings. This might include a TXT record or a CNAME record that Validity (or the FBL provider) can query to confirm ownership. This method is particularly relevant for FBLs that allow DKIM-based signup, where the complaint data is tied to the DKIM signing domain rather than the sending IP. Some FBL partners may not support DKIM-based signup, so it's important to verify this with Validity.
For instance, to validate a domain, you might be asked to add a TXT record like this:
If you are an ESP client and manage your own sending domains (i.e., you are not sending from a shared ESP domain), you would typically need access to your domain's DNS settings to add these records. If your ESP manages your domain's DNS, they would need to implement these changes on your behalf. This highlights the importance of collaboration between clients and their ESPs, especially concerning email authentication and validation. You can explore more about how ESPs collect Yahoo FBL data and the specific DNS records required for Yahoo's Complaint Feedback Loop.
Client vs. ESP roles in FBL management
The choice between client-direct signup or ESP-managed FBLs largely depends on the client's technical capabilities and the specific setup of their email sending. For senders using shared IPs provided by their ESP, it's almost always the ESP that handles FBL enrollment. This is because the IP reputation, and thus the FBL data, is shared across multiple clients using that IP. If you are a client and wish to receive FBL data directly, you generally need to be sending from dedicated IPs or have full control over your sending domains.
If an ESP is already signed up for Validity FBLs, it's generally not possible for them to simply delegate access for specific IPs to their clients if the client isn't the direct owner or controller of those IPs. However, if the same IP needs to exist on multiple accounts (e.g., an ESP account and a client account for a specific brand), it can be allowed as long as all accounts are able to validate ownership. This is often more feasible with domain-based validation, where multiple entities can have records pointing to the same sending infrastructure if necessary.
For ESPs, a crucial aspect of managing client deliverability is ensuring that their clients' domains are properly authenticated and that FBLs are utilized effectively. This includes advising clients on how to handle email authentication and monitoring their email domain reputation. Being listed on a blocklist (or blacklist) can severely impact deliverability, making FBL data indispensable for proactive management.
Client-managed FBL signup
Direct control: Clients have full access to FBL data specific to their campaigns.
Requires dedicated resources: Clients must manage IP/domain validation and process FBL data internally.
Suitable for: Large senders with their own infrastructure or advanced technical teams.
While Validity FBLs (and FBLs in general) are invaluable for understanding complaint rates, they are just one piece of the deliverability puzzle. Senders must also focus on broader email deliverability best practices to ensure their messages reach the inbox consistently. This includes maintaining a clean mailing list, sending relevant content, and ensuring proper email authentication (SPF, DKIM, DMARC).
Monitoring your IP and domain reputation is also critical. Tools like blocklist monitoring and DMARC reporting can provide comprehensive insights beyond FBL data alone. Regularly checking if your sending IPs or domains are on any blacklist (or blocklist) is a proactive step to prevent deliverability issues. Additionally, implementing strong DMARC policies helps protect your brand from spoofing and provides valuable feedback on authentication failures, contributing to overall domain health.
The collaboration between ESPs and their clients is vital for optimal email performance. While ESPs offer foundational services and often manage complex technical integrations, clients also have a role in maintaining good sending practices and understanding the data provided by FBLs and other deliverability tools. This combined effort ensures that email programs are robust and effective.
Views from the trenches
Best practices
Actively monitor your FBL data and complaint rates to identify potential issues early and address them promptly.
Ensure your DNS records (SPF, DKIM, PTR) are correctly configured and aligned with your sending domains for strong authentication.
Regularly clean your email lists to remove inactive or problematic subscribers, reducing the likelihood of spam complaints and spam trap hits.
Segment your audience and tailor content to improve engagement and reduce unsubscribe rates, which positively impacts sender reputation.
Common pitfalls
Assuming your ESP handles all FBLs automatically, without verifying which ones or how data is shared.
Not understanding the difference between IP-based and domain-based FBL validation and its implications for direct client signup.
Ignoring FBL data, leading to unchecked spam complaints and subsequent negative impacts on deliverability and reputation.
Failing to maintain proper email authentication records, which can prevent FBL signup and worsen inbox placement.
Expert tips
Consider engaging with your ESP to understand their FBL enrollment practices and how they can provide complaint data relevant to your specific sending.
For direct client signup, confirm you have the necessary technical access and expertise to manage DNS records for IP/domain validation.
Even if your ESP manages FBLs, actively review any reports or insights they provide to stay informed about your complaint rates.
Explore other deliverability tools and metrics alongside FBL data for a holistic view of your email program's health.
Marketer view
Marketer from Email Geeks says anyone can sign up for Validity FBL if they are willing to pay and can validate that the IP addresses or domains are under their control.
May 8, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks confirms that senders can directly sign up for Validity FBL.
May 8, 2024 - Email Geeks
Final thoughts on FBL enrollment
In summary, ESP clients can indeed sign up for Validity FBLs, provided they can demonstrate control over the IPs or domains they wish to register. This validation is typically achieved through proper configuration of PTR records for IPs or specific DNS records (like TXT or CNAME) for domains, often related to DKIM. While ESPs frequently manage FBL registrations on behalf of their clients, direct enrollment is an option for those with the necessary technical control and expertise.
The key takeaway is that effective email deliverability, including leveraging FBLs, requires a collaborative effort between senders and their service providers. Whether managed directly or through an ESP, access to spam complaint data is crucial for maintaining a strong sender reputation and ensuring your emails consistently reach the intended inbox.
