The implementation of SPF (Sender Policy Framework) prevents spamming, phishing, and spoofing attacks while also ensuring that the email deliverability rate of your domain is decent. SPF evaluation lets email messages dispatched only by trusted and specified sending IP addresses (ipv4 and ipv6) reach the inboxes of desired recipients. Configurations of an SPF record instruct recipients’ mail servers to mark emails coming from an unspecified array of sending source set as either spam or reject their entry.
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However, an SPF record has high odds of having temperrors (temporary errors) and permerrors (permanent errors) that impede SPF, DKIM, and DMARC email authentication processes. One of the common causes of an SPF permerror is the SPF too many DNS lookups issue. Let’s see what it is and tips to fix it.
Starting from the Scratch- What is an SPF Lookup?
An SPF lookup is the process where an email server looks into the DNS record of the sender’s domain to confirm if a particular IP address is authorized to send emails on behalf of your company or not. But, there’s a limit of a maximum of 10 DNS lookups; exceeding it causes SPF too many DNS lookup errors.
Permerror; SPF Permanent Error Too Many DNS Lookups
Receivers’ mail servers retrieve SPF records to verify if a particular sender is allowed to send messages using the domain of a business. The limit on these DNS lookups is placed to prevent overloading resources used in extracting SPF TXT records which can otherwise cause delayed operations and responses.
This is because when a mail server tries retrieving an SPF DNS record corresponding to the sender’s domain, it performs DNS queries with multiple DNS servers. So, if there’s no concept of the DNS lookup count, a cyberattack expert can potentially flood the system with traffic of multiple DNS queries, which results in the crashing of the system.
The Primary Reason Why SPF Lookup Limit is a Challenge for Domain Owners and Administrators?
As much as the concept of the DNS lookup limit helps keep hackers at bay, it also poses a significant challenge for domain owners and administrators to stay within it. Exceeding the limit of a maximum of 10 DNS lookups causes an SPF permerror that makes your SPF TXT record go invalid, exposing your email-sending domain and server to the malicious intentions of cyber actors.
Moreover, the instances of false negatives make the situation worse. Here are some common reasons adding up to the challenge-
1. A Number of Services and Third-Party Vendors
Organizations often outsource marketing, PR, customer support, analytics, and other operations. Each vendor or service provider might have their own SPF records for IPs and domains, making way for the issue of a maximum lookup limit of 10.
2. Nested SPF Records
An SPF record including mechanisms like include, a, ptr, or mx refers to other domains’ SPF records, piling up a string of DNS lookups with each subsequent lookup adding up to the overall count and creating a problem. In this way, a single SPF email authentication record can result in a number of DNS lookups and pose a challenge to email deliverability.
3. Complex SPF Setups
Avoid using the “include” mechanism, complex modifiers, and expansive IP address list, as they cumulate towards more DNS lookups, and result in a synchronization risk for partner domain and hostname owners.
4. Email Forwarding
An independent DNS query is made on each instance of cross-domain email forwarding.
5. Wrong Configuration of SPF Records
Broken SPF mechanisms and improper configurations result in an unsuccessful response to DNS queries or a failed SPF check. This prompts a recipient’s server to perform more lookups in an attempt to validate the message.
6. Inconsistent Practices
Not all organizations fully understand the implications of SPF lookup limits, leading to improper SPF record configurations or overlooking the cumulative effect of multiple lookups.
How SPF Flattening or SPF Compression Helps Fix the Error?
SPF flattening is the process of compressing the SPF record in question. The consolidated record is then published in your domain’s DNS for an unhampered email authentication process. It works by-
- Merging multiple mechanisms, directives, and modifiers.
- Eliminating redundant entries to get a simpler and cleaner TXT record as a result.
The practice of SPF record flattening helps resolve the “SPF Too Many DNS Lookups” issues by terminating the need for email receivers to perform more than one lookup.
Importance of SPF Record Flattening
Consolidated SPF records support the idea and practice of proper testing before its deployment in the DNS. The whole practice imparts the following benefits-
Better Email Authentication
DNS records are the basis of the SPF authentication process, and no permerror means no delays in the SPF specification.
No Lookup Limit Error
This practice fixes one of the core permerror issues by preventing “too many DNS lookups,” which can otherwise cause email delivery and SPF email authentication issues.
There’s a consistent SPF specification throughout sources, statements, and mechanisms.
High Email Delivery
SPF record flattening resolves TXT record problems that subsequently ensures most of your emails land in the inbox section of mailboxes.
Improved Sender Reputation
A low number of spam and bounced emails boost the sender’s reputation of your domain, as email service providers or ESPs (for example; Gmail and Microsoft Outlook) trust them.
The Underrated Role of Multiple SPF Records in Exceeding the DNS-Lookup Limit
The existence of multiple SPF records leads to a cumulation of DNS queries pulled out by each record as associated mechanisms. Domain owners create multiple SPF records with the idea of enhancing email security, but improper management and development cause unintended problems in the way.
This throws light on the importance of proper SPF record configuration, potential utilization of SPF flattening or compression techniques, and regular SPF check drill to ensure you don’t fail to meet compliance with the lookup limit and have improved email deliverability. An SPF record checker highlights wrong SPF settings and suggests required changes to stay in place.
SPF Lookup Counter
The SPF lookup counter is a reference made to a set of tools that helps maintain a tally of the DNS lookups performed during the SPF validation process. This solution ultimately helps stay within the limit of DNS queries.
The SPF lookup count information and an SPF checker can be collectively exercised for fixing existing errors in an SPF record of your domain and streamlining the authentication process through DKIM and DMARC while also ensuring no ESP identifies you as a suspicious sender.
An SPF TXT record includes ip4 and ip6 address ranges that are allowed to send emails on behalf of your company. It also uses mechanisms, modifier, and qualifiers that are collectively called SPF syntax. The whole process of SPF specification acts as a solution for email delivery and enhances email security by also streamlining DKIM and DMARC operations so that verification doesn’t fail in any steps.
The SPF DNS-lookup limit of 10 is a permerror whose solution comes in the name of SPF flattening or compression where unnecessary include statements, and use of the ptr mechanism is taken to another side. All references and implementations of the “include” statement are counted towards this limit.
Reach out to us for safe SPF implementations as per RFC7208.