SPF Record Limits
Avoid breaking email authentication with too many lookups
Back to Email & ReputationWhat we check
We detect if your SPF record exceeds the DNS lookup limit
We detect if your SPF record exceeds the 10 DNS lookup limit. Each include:, a:, mx:, and redirect: mechanism in your SPF record counts as a lookup. Exceeding 10 lookups causes complete SPF validation failure, breaking email authentication for all your messages.
Security Impact
Why SPF lookup limits are critical
Complete SPF failure
Exceeding 10 DNS lookups causes ALL your emails to fail SPF validation. This is not a soft failure—SPF completely breaks, even for legitimate emails.
Massive deliverability damage
When SPF fails, receiving servers reject or spam your emails. This destroys deliverability and sender reputation, potentially affecting thousands of messages.
Silent and sudden failure
SPF limit violations often happen gradually as you add email services. You might not notice until deliverability suddenly tanks.
Difficult to diagnose
Most email testing tools don't clearly report SPF lookup limits. You might waste days debugging deliverability issues without realizing SPF broke.
Implementation
How to fix SPF lookup limit issues
With Httpeace
Httpeace automatically counts DNS lookups in your SPF record:
- Add your domain to Httpeace
- We check SPF lookup count automatically every day
- Get instant alerts when approaching or exceeding the 10 lookup limit
- See which includes contribute to your lookup count
Without Httpeace
Manual SPF lookup counting requires understanding nested includes:
# Online validators # Visit: https://www.kitterman.com/spf/validate.html # Visit: https://mxtoolbox.com/spf.aspx # Manual counting (tedious) dig TXT yourdomain.com | grep spf dig TXT _spf.google.com | grep spf dig TXT _spf.mailgun.org | grep spf # Continue for each nested include...
You'll need to:
- Understand which mechanisms count as lookups (include:, a:, mx:, redirect:)
- Manually resolve each include: to count nested lookups
- Track lookup counts across multiple levels of nesting
- Contact email providers for their current IP ranges
- Convert include: statements to ip4:/ip6: addresses where possible
- Maintain IP address lists as providers change infrastructure
- Consider SPF flattening services (AutoSPF, PowerSPF, EasySPF)
- Evaluate costs vs complexity of flattening services
- Audit and remove unused email service includes
- Consolidate email sending through fewer providers
- Use subdomains to split email types (marketing.domain.com)
- Test SPF after every change to ensure under 10 lookups
- Monitor for provider changes that add lookups
- Document SPF structure for team reference
- Set up alerts before hitting the limit
SPF lookup counting is incredibly tedious and error-prone. Nested includes hide the true lookup count, and providers can add lookups without notice. Exceeding 10 lookups causes instant, complete SPF failure for all emails.
FAQ
Frequently asked questions
Why is there a 10 lookup limit?
The 10 lookup limit prevents SPF from causing excessive DNS queries and potential denial-of-service situations. It was defined in the original SPF RFC and cannot be changed. Exceeding it causes immediate failure.
Do nested includes count multiple times?
Yes! If you include: a domain that itself includes other domains, ALL those lookups count toward your limit. This is why services like SendGrid or Mailchimp can consume 3-5 lookups by themselves.
What happens at exactly 10 lookups?
At 10 lookups, SPF still works. At 11 or more, SPF validation fails completely with "permerror". All your emails immediately fail SPF, even legitimate ones from authorized servers.
Can I split SPF across subdomains?
Yes! A great strategy is using subdomains for different email types. For example, use marketing.yourdomain.com for marketing emails and support.yourdomain.com for support. Each subdomain gets its own 10-lookup budget.
How often does Httpeace check SPF lookup limits?
We check your SPF record daily and count all DNS lookups, including nested includes. We alert you when you approach or exceed the 10 lookup limit, before it breaks your email deliverability.
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