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SPF include: Explained — What It Does and When to Use It
include:vendor.net tells the receiver: “also evaluate that domain’s SPF.” It is indirection — not a magic CC list.
Lookup math
Each mechanism that triggers DNS counts. Nested includes multiply pain. That is why stacks with six SaaS tools blow past ten without anyone editing a character.
v=spf1 include:_spf.google.com include:sendgrid.net ~all
Learn more: SPF record, SPF guide.
FAQ
Does include pull IPs automatically at send time?
No — receivers resolve the included SPF record at lookup time; nested includes chain.
Why is nested include expensive?
Each include: can add more lookups — SendGrid’s record includes more includes.
What is the limit?
10 DNS lookups total for SPF evaluation — see the SPF lookup limit post on this blog.
Can I replace include with ip4?
Yes — flattening — trades operational pain for fewer lookups.
How do I count?
DNS Preflight SPF tree shows the running total.