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Resolve all SPF includes into IP addresses, visualize your lookup count, and generate a flattened record that stays under the 10-lookup limit.
Enter a domain to resolve all SPF includes, count DNS lookups, and generate a flattened record.
SPF flattening takes your SPF record and recursively resolves all include:, a:, and mx: mechanisms into their underlying IP addresses. The result is a "flat" SPF record that uses only ip4: and ip6: mechanisms, requiring zero DNS lookups to evaluate.
RFC 7208 limits SPF evaluation to 10 DNS lookups. Each include:, a:, mx:, redirect=, and exists: mechanism counts as one lookup. Nested includes count too. If your record exceeds 10, receiving servers return a PermError and SPF fails — potentially causing your emails to be rejected or flagged as spam.
You should consider flattening when your SPF record has more than 7-8 lookups, or if you use multiple email services (Google Workspace, Microsoft 365, SendGrid, Mailchimp, etc.) that each add their own include: directives. Organizations using 3+ email providers commonly hit the 10-lookup limit.
IP addresses can change. When your email providers update their infrastructure, the IPs in your flattened record become stale. You need to re-flatten regularly (weekly or monthly) or use a dynamic flattening service. A stale flattened record can cause legitimate emails to fail SPF checks.
Unboxd reads every email and gives you a daily briefing with only what matters.