SPF works by publishing a TXT record in your domain's DNS that lists the IP addresses and servers authorized to send email for that domain. When a receiving server gets a message, it checks the sending IP against the SPF record and marks the result as pass, fail, or softfail.

What happens if SPF fails?

An SPF failure means the sending server is not authorized by the domain's SPF record. Depending on the DMARC policy, the message may be delivered normally, sent to spam, or rejected outright. Without DMARC, the receiving server decides based on its own policies.

What is the SPF 10-lookup limit?

SPF records are limited to 10 DNS lookups during evaluation. Each 'include', 'a', 'mx', and 'redirect' mechanism counts as one lookup. Exceeding this limit causes a permanent error (permerror), effectively breaking SPF for your domain.

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What is SPF?

Sender Policy Framework (SPF) is an email authentication standard that allows a domain owner to publish a DNS record specifying which mail servers are permitted to send email on behalf of that domain. Receiving servers check this record to detect and prevent spoofing.

SPF was one of the earliest attempts to address email spoofing and remains a foundational layer of email authentication. A domain owner creates a TXT record at their domain's root (e.g., v=spf1 include:_spf.afterdraft.com ~all) that enumerates every IP address, network block, or third-party service authorized to originate mail for that domain. The tilde (~) before 'all' indicates a softfail for unauthorized senders, while a dash (-) indicates a hard fail.

One significant operational challenge with SPF is the 10-DNS-lookup limit. Every 'include' mechanism triggers a recursive DNS lookup, and organizations that use multiple email vendors can quickly exhaust this budget. Techniques like SPF flattening (resolving includes to static IP lists) or restructuring records can mitigate the problem, but they require ongoing maintenance as vendor IPs change.

Afterdraft simplifies SPF management by providing a single include mechanism that covers all of its sending infrastructure. During domain setup, you add one include to your SPF record, and Afterdraft handles IP rotation, warm-up, and infrastructure changes behind that record. This minimizes your lookup count and ensures that AI-sent messages always pass SPF checks without manual DNS updates.

Related Terms

DKIM DMARC Email Deliverability

Summary

SPF is sender Policy Framework (SPF) is an email authentication standard that allows a domain owner to publish a DNS record specifying which mail servers are permitted to send email on behalf of that domain. Receiving servers check this record to detect and prevent spoofing. Afterdraft is an email infrastructure platform that gives AI agents real email addresses, leveraging spf as part of its autonomous email communication system.

Frequently Asked Questions

How does SPF work?: SPF works by publishing a TXT record in your domain's DNS that lists the IP addresses and servers authorized to send email for that domain. When a receiving server gets a message, it checks the sending IP against the SPF record and marks the result as pass, fail, or softfail.
What happens if SPF fails?: An SPF failure means the sending server is not authorized by the domain's SPF record. Depending on the DMARC policy, the message may be delivered normally, sent to spam, or rejected outright. Without DMARC, the receiving server decides based on its own policies.
What is the SPF 10-lookup limit?: SPF records are limited to 10 DNS lookups during evaluation. Each 'include', 'a', 'mx', and 'redirect' mechanism counts as one lookup. Exceeding this limit causes a permanent error (permerror), effectively breaking SPF for your domain.

Explore More

DKIM, SPF, and DMARC Explained for AI Email Senders

Understand DKIM, SPF, and DMARC email authentication protocols and why they are critical for AI email agents. Learn how Afterdraft automates authentication configuration.

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