When you send an email, the receiving mail server needs a way to check if it really came from your domain. That is where SPF comes in.
But sometimes, things get messy, and you may see an error called SPF too many DNS lookups. This happens when your SPF record asks the server to check more DNS information than allowed. The limit is 10 lookups, and it exists to keep email systems fast and safe. Once your SPF record crosses that limit, mail services may stop trusting your messages. They might send them to spam or block them completely.
If you use many email tools for marketing, support, or billing, this problem can appear without you even noticing. In this guide, you will learn why it happens and how to fix it.
What Does ‘SPF Too Many DNS Lookups’ Mean
As per RFC 7208, there can not be more than 10 DNS lookups per SPF record. The error ‘SPF too many DNS lookups’ means your SPF record is trying to check more than 10 DNS entries when an email is verified.
SPF works by confirming which servers are allowed to send emails for your domain. To do this, it looks up DNS information linked to mechanisms like include, a, mx, and exists. Each of these can trigger one or more DNS queries. If the total number goes beyond 10, the receiving mail server stops checking and treats your SPF record as invalid.
This error can cause your emails to fail authentication and land in spam or get blocked. The problem usually occurs when you add many email services, and each of them adds extra lookup requirements in your SPF record.
Sometimes the limit is crossed without you noticing, which makes the problem harder to detect. So, it’s suggested that you regularly run your SPF record through an SPF record lookup tool.
Why SPF Has a 10 DNS Lookup Limit
Here are three reasons why RFC has imposed the SPF record too many DNS lookups limit in the first place-
1. Reduce the Load on the DNS Server
Every lookup asks a DNS resolver to search for records and return the data. This puts a load on the DNS server. So, if a single SPF record triggers a large chain of queries, it puts pressure on DNS systems and slows responses for everyone. That’s why, by limiting SPF to 10 lookups, the DNS traffic becomes predictable.
2. Prevents Delays in Email Deliveries
Too many DNS lookups increase the time it takes to verify an email. Mail servers have to wait for each lookup before deciding if a message is safe. With the imposition of the limit, the latency is reduced, which ultimately helps emails move faster through filters. This way, messages don’t get stuck or rejected.
3. Protects Against Security Risks
If there is no limit, attackers could create SPF records that force many DNS requests and slow down or crash mail systems. But with the presence of the limit, their tactics are blocked, helping domain owners avoid DDoS attacks.
Reasons For ‘SPF Too Many DNS Lookups’ Error
Usually the reasons for this error are well within the control of the person in charge of maintaining the SPF record. Let’s see the possible reasons first and then know how can you fix them.
Complex SPF Records
One of the common things triggering this error is an over-crowded SPF record. Whenever you use mechanisms like include, a, mx, ptr, and exists, each instance of their occurrence gets counted towards the DNS limit. So, as your SPF record grows, a point comes when the SPF record requires too many DNS lookups for a complete evaluation.
Too Many ‘include’ Statements
The SPF record too many DNS lookups problem often appears when there are too many ‘include’ statements. Each ‘include’ pulls in another SPF record, which can also contain more ‘include,’ ‘a,’ and ‘mx’ mechanisms. This creates a chain of DNS queries.
If every included record is large or badly managed, the combined SPF policy quickly reaches the 10 lookup cap. This is all the more possible when you have included multiple third-party service providers that send emails on your behalf.
Extra Domains and Fragmented Policies
If your organization owns multiple domains and subdomains, and has created individual SPF records for each, then too many DNS lookups are inevitable. In some cases, email forwarding or alias setups can cause a single message to trigger SPF checks on multiple domains. This results in adding more DNS activities, increasing the risk of an SPF record requiring too many DNS lookups.
How to Check SPF for Too Many DNS Lookups
Finding out whether your SPF record has exceeded the 10 DNS lookup limit is not as mysterious as it sounds. Here are simple ways to check it:
1. Use an Online SPF Lookup Checker
An SPF lookup tool can count all DNS lookups in your SPF record and tell you if it hits the dreaded ‘SPF record requires too many DNS lookups limit’ error. It breaks down mechanisms like include, a, mx, and nested records, so you see exactly where the lookups are coming from.
2. Count Lookups Manually
Start with your main SPF record, count lookup mechanisms (include, a, mx, exists, and ptr), then open every included SPF record and repeat. If the total goes beyond 10, you have a ‘too many DNS lookups’ issue.
3. Check Your DMARC Reports
If your SPF is already failing, DMARC reports may show a Permerror for SPF. This often happens when the lookup limit is crossed. So if you see Permerror often, it is a clue that your SPF record needs fixing.
You can use DMARC XML Report Analyzer to convert the report data into easy-to-understand format.
How to Fix the ‘SPF Too Many DNS Lookups’ Error
Here is how to fix SPF too many DNS lookups by making your SPF record lighter and easier to evaluate.
- Reduce ‘include’ Statements
The ‘include’ statements tells the mail server to check another domain’s SPF record. If you have too many ‘include’ occurences, the DNS lookup count increases. Remove any include statements you do not need and replace them with other mechanisms when possible.
- Use ip4 and ip6 Mechanisms
If your SPF record has one ‘include’ to allow a few IP addresses, it’s best you remove it and use ip4 or ip6 mechanisms to directly add the IPs. This will cut down on extra checks and keep your record simpler.
- Flatten Your SPF Record
Flattening means changing mechanisms like ‘include’ into direct IP addresses. This reduces DNS queries because the mail server does not need to look up more SPF records. Some tools can do SPF flattening automatically.
- Remove Redundant Mechanisms
Sometimes one ‘include’ already covers another ‘include’ or mechanism. If two parts give the same result, delete one of them. This prevents extra DNS lookups and lowers the risk of errors.
- Remove ‘ptr’ Mechanisms
The ‘ptr’ mechanism is no longer recommended because it creates many DNS lookups and slows down SPF checks. Avoid using ‘ptr’ in your SPF record.
- Delete Reference to Unused Domains
If you stop using an email service or a vendor, remove their domain from your SPF record. Keeping old or unused entries adds unnecessary DNS lookups, which leads to more than 10 lookups.
Keeping Your SPF Lookup Count Under Control
Fixing the SPF record too many DNS lookups problem is an important step in protecting your domain and improving email deliverability. When your SPF record stays within the 10 lookup limit, mail servers can verify your messages faster and trust your domain more. This reduces the chances of your emails being rejected or marked as spam. Regular monitoring, flattening, and cleaning unused include statements will help you avoid the SPF too many DNS lookups error in the future.
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Frequently Asked Questions
This error appears when your SPF record forces a mail server to make more than 10 DNS checks. SPF uses DNS lookups to confirm which servers can send emails for your domain. If the record triggers too many lookups, the server may stop checking and mark the email as suspicious. This can lead to failed SPF authentication and lower email deliverability, which means more emails landing in spam folders.
Your SPF record may exceed the limit when you use too many include, a, mx, exists, or ptr mechanisms. Each of these can trigger DNS lookups. This usually happens when a domain uses multiple email platforms, such as marketing, support, or billing tools. If every service adds its own include statement, the SPF record grows and eventually crosses the 10 DNS lookup limit, causing a Permerror.
You can use an online SPF checker tool to count the DNS lookups in your record. The tool breaks down all include, a, mx, ptr, and exists mechanisms so you can see where the lookups come from. You can also check your DMARC reports for SPF Permerror. If you want to do it manually, you must review your SPF record and each included record to count every lookup.
You can fix the issue by removing unnecessary include statements, using ip4 and ip6 mechanisms for direct IP ranges, and flattening your SPF record to replace complex parts with IP addresses. You should also delete ptr and clean old or unused vendor entries. The goal is to reduce DNS queries so your SPF record stays within the 10 lookup limit and passes authentication without failing.
If you do not fix this issue, mail servers might fail to verify your emails. This increases the chances of messages going to spam or being rejected completely. Over time, your domain reputation can drop, and email deliverability becomes weaker. This affects marketing campaigns, customer communication, and security alerts. Fixing the SPF record early helps keep your domain trusted and your email channels reliable.
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