SPF Record Flattener & Lookup Optimizer
Recursively resolve nested include: domains, collapse overlapping IPv4/IPv6 CIDR blocks, and flatten your Sender Policy Framework (SPF) DNS record to prevent exceeding the strict 10 DNS lookup limit (RFC 7208).
What Is the SPF 10-Lookup Limit (RFC 7208)?
Section 4.6.4 of RFC 7208 mandates that receiving mail servers must limit the number of DNS lookups performed during SPF evaluation to a maximum of 10 DNS queries (including include:, a, mx, ptr, and redirect mechanisms).
Why Exceeding 10 Lookups Causes Email Delivery Failure
If evaluating your domain's SPF record requires more than 10 DNS queries (which frequently occurs when combining Google Workspace, Microsoft 365, Salesforce, Zendesk, and HubSpot inclusions), receiving mail servers return a PermError (Permanent Error) and fail SPF authentication for your outbound email.
How SPF Flattening Works
SPF flattening queries all nested include: domains client-side, extracts the underlying ip4: and ip6: CIDR address ranges, removes duplicate subnets, and replaces nested domain references with explicit IP network blocks. This reduces total evaluation DNS queries to 1 (the initial TXT query for your domain).