Why does SURBL form say 'Lookup and requested host do not match'?
Michael Ko
Co-founder & CEO, Suped
Published 22 May 2025
Updated 16 Aug 2025
8 min read
When you are trying to delist a domain or IP address from a blocklist, encountering an error message like "Lookup and requested host do not match" can be incredibly frustrating. This specific message often appears when interacting with the SURBL lookup form, and it indicates a fundamental misunderstanding between what you are providing and what the system expects. It's a common stumbling block for many, and it boils down to how SURBL processes requests versus how users perceive their input.
The core of the issue usually lies in the distinction between an IP address and a domain name, and sometimes even the specific format or type of domain being entered. While you might be focused on removing your domain from a blacklist, the SURBL system performs specific DNS lookups, and if the data you provide doesn't align with their expected lookup format, it will trigger this mismatch error. Understanding this distinction is the first step to successfully navigating the delisting process.
SURBL, like other DNS-based blocklists (DNSBLs), operates by listing domains that appear in spam messages. These aren't always the sending domains, but often the domains found in the body of emails, such as those linked in URLs. When you submit a query to the SURBL form, it expects a specific type of input to perform its reverse DNS or direct DNS lookup.
The SURBL system is primarily concerned with domains, not necessarily the IP addresses that host those domains or send email from them directly. This can be confusing, especially if you are used to checking IP-based blacklists. The error "Lookup and requested host do not match" often means that the system couldn't perform the expected DNS resolution on the input you provided because it wasn't in the correct format or type for a domain lookup.
For example, if you enter an IP address where a domain name is expected, or vice versa, the system won't find a corresponding DNS record that matches its lookup logic. It’s critical to understand that SURBL is a blocklist for domains, specifically those that are part of spam URLs or host malicious content. If you are dealing with an IP-based blacklist (or blocklist) issue, SURBL is not the right tool for that particular delisting, and you would likely encounter this kind of error. We have other resources that explain how email blacklists work and what a DNSBL is if you need more clarity.
SURBL's focus
SURBL mainly lists domains, not IP addresses. It’s critical to provide a fully qualified domain name (FQDN) like example.com or mail.example.com, not an IP address.
Common causes of the mismatch
The most frequent reason for this error is simply providing the wrong type of identifier. If the SURBL form is asking for a domain, and you input an IP address, you'll get this message. Conversely, if it somehow expects an IP and you give it a domain, the same problem arises. This is particularly common if you're used to checking IP blocklists like Spamhaus PBL or Spamhaus SBL-XBL.
Another cause can be issues with DNS resolution itself. If the domain you're trying to look up doesn't have proper A records pointing to its IP, or if its DNS is misconfigured, SURBL's lookup process might fail, resulting in the mismatch error. This isn't necessarily a listing issue but a technical one preventing the check from completing. For instance, if your domain's authoritative name servers are down or slow, the SURBL system might time out when trying to resolve the domain.
Also, consider whether you're checking the root domain (e.g., example.com) versus a subdomain (e.g., tracking.example.com). SURBL listings are often very specific to the subdomain found in spam, so make sure you're querying the exact host that is causing the problem. If you enter example.com when the actual listing is for marketing.example.com, the system will report a mismatch because the requested host (the root domain) doesn't match the one it expects to find (the subdomain).
Example DNS queriesBASH
dig +short example.com A
dig +short 192.0.2.1.zen.spamhaus.org
Troubleshooting steps for host mismatch
To troubleshoot this error, your first step is to confirm the exact domain or IP that you believe is listed. Sometimes, the problem lies not in the SURBL form itself, but in accurately identifying the entity that is actually blocklisted. You can use a general blocklist checker to verify.
Next, ensure your DNS records are correctly configured and propagating. Check your domain's A records to ensure they point to the correct IP addresses. If you're dealing with an IP that's suspected of being tied to a domain listing, make sure reverse DNS (PTR) records are set up properly for your sending IP addresses and resolve back to the expected domain. A common issue is a generic reverse DNS (RDNS) that doesn't match your brand, which can lead to deliverability problems and even blocklist inclusion, as discussed in our guide on why your IP might be listed due to generic RDNS.
Finally, double-check the SURBL form instructions carefully. The error message explicitly states "Lookup and requested host do not match," implying that the value you entered (the "requested host") is not what their system (the "lookup") expects for a successful match. This might mean you need to enter the specific malicious URL or domain that was identified in the spam, rather than your main company domain. Remember that SURBL's listings can affect deliverability to major providers like Gmail, making accurate delisting crucial.
Common input pitfalls
IP address entered: Providing an IP (e.g., 192.0.2.1) when a domain is expected.
Incorrect domain format: Entering a URL path (e.g., example.com/spamlink) instead of just the domain.
Misidentified host: Querying the root domain when a specific subdomain (e.g., img.example.com) is actually listed.
Effective solutions
Use domain only: Always provide only the domain name (e.g., example.com) unless specifically asked for an IP.
Check DNS records: Verify your domain's A records and any relevant PTR records are correct.
Specify exact host: Enter the precise domain or subdomain that was involved in the spam.
Advanced considerations for delisting
Sometimes, the "Lookup and requested host do not match" error can be a symptom of a deeper issue, such as shared email infrastructure. If you're sending email through a shared platform, your domain's reputation can be impacted by other users on the same IPs. While SURBL focuses on domains, an associated IP's poor reputation or generic reverse DNS could indirectly cause issues with how your domain is perceived or how lookups resolve. We have specific guidance on troubleshooting SURBL listings for shared infrastructure.
When facing persistent issues, understanding how to contact SURBL for support becomes important. Their website often provides specific instructions for delisting. Always follow their stated procedures precisely, as deviations can lead to further delays or confusion, manifesting in errors like the host mismatch.
It's also worth noting that automated lookups or scripts attempting to query the SURBL system incorrectly can trigger this message as a protective measure. Always use the official web form for manual checks rather than attempting programmatic access unless explicitly allowed. This ensures you're interacting with their system as intended. Proper email authentication protocols like DMARC, DKIM, and SPF are also crucial for maintaining a good sender reputation and avoiding blocklists. Tools like our free DMARC record generator can help you set up these records correctly.
Even with a 100% opt-in list, you can still get blocklisted, especially by SURBL's CT blacklist, if your domain is found in suspicious URLs or content. This highlights why continuous monitoring and proactive measures are so important.
Input type
Expected format
Likely SURBL response
Domain name
example.com or sub.example.com
Listing status (if found), or no match
IP address
192.0.2.1
“Lookup and requested host do not match” (if domain expected)
Full URL
http://example.com/path
“Lookup and requested host do not match” (if domain expected)
Resolving the SURBL host mismatch
The phrase "Lookup and requested host do not match" from SURBL is a clear signal that the input you provided does not align with what their system is designed to process. It's not a direct confirmation of a blacklist listing, but rather an indication that the query itself is malformed or targeting the wrong type of identifier.
Always remember that SURBL lists domains, not IPs. Ensuring you provide a proper fully qualified domain name (FQDN) and verifying your DNS records are in order are crucial first steps. If you continue to face challenges, consulting SURBL's documentation or their direct support channels can provide the specific guidance needed for your situation. Persistence and attention to detail are key to successfully navigating blocklist issues.
Views from the trenches
Best practices
Always use the official SURBL lookup form for queries, avoiding automated scripts.
Verify the exact domain or subdomain that is potentially blocklisted before submitting.
Ensure your domain's DNS records (A, CNAME) are correctly configured and propagated.
Understand that SURBL focuses on domains, not IP addresses, when performing lookups.
Common pitfalls
Entering an IP address instead of a domain name on the SURBL form.
Querying the root domain when a specific subdomain is listed (e.g., mail.example.com).
Ignoring the specific error message, which indicates an input mismatch, not a listing.
Assuming all blocklists work the same way, leading to incorrect input formats.
Expert tips
Double-check that the domain you're entering into the SURBL form is exactly what you suspect is listed, including any subdomains.
Verify your domain's DNS resolution to ensure it's publicly accessible and configured correctly.
If you're dealing with a shared hosting environment, recognize that others' actions can affect your domain and require different troubleshooting approaches.
For persistent issues, review SURBL's FAQ and removal policies directly on their website.
Marketer view
Marketer from Email Geeks says they were confused about the SURBL form asking for a 'host' when they were trying to delist a domain, which caused a mismatch error.
2021-12-16 - Email Geeks
Expert view
Expert from Email Geeks says the lookup form usually works without issues for them, suggesting the input might be the problem.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Gmail, making accurate delisting crucial.
