SPF records are obligated to stay within the SPF DNS lookup limit of 10, otherwise, Permerror occurs. An SPF Permerror invalidates the SPF record, causing email deliverability and authentication problems for messages sent on behalf of your company. This gives hackers the opportunity to execute phishing and spoofing attacks using your domain.
An SPF lookup counter gives you an overview of your record’s condition, giving you a heads-up when it’s about to cross the DNS lookup limit and cause errors.
Email deliverability checklist
Image sourced from mailtrap.io
How does the SPF Lookup Counter Control SPF Lookups?
An SPF record includes multiple mechanisms and modifiers that instruct recipients’ servers how to treat illegitimate emails coming from your domain. An SPF lookup counter minimizes the number of DNS lookups a receiving server will perform to validate an SPF record. Since each DNS lookup uses resources, a limit of a maximum of 10 SPF DNS lookups is imposed to avoid delays in email transmissions. If this limit is exceeded, the messages are identified as suspicious.
How is the Number of SPF Lookups Counted?
Let’s consider an example of SPF records to comprehend how SPF lookups are counted. Suppose an organization owns 3 domains; domain1.com, domain2.com, and domain3.com. You will come across the following upon an SPF lookup-
v=spf1 include:_domain1.com include:_domain2.com include:_domain3.com ~all
Each of the included _domainX SPF records conveniently lists IP addresses, eliminating the need for additional domain lookups.
Now, in this case, the total lookup count will be three, one for each record.
While there are alternative methods to circumvent the common issue of SPF causing excessive DNS lookups, employing the SPF lookup counter offers a proactive approach to determining lookup counts in advance. As the saying goes, it’s better to err on the side of caution!