Level: Intermediate
SPF enforces a hard limit of 10 DNS lookups during evaluation, and exceeding it causes the entire SPF check to fail, a common and often overlooked technical trap.
Every Include Mechanism Counts Toward the Limit
Each third-party service added via an include mechanism, and any nested includes within those services' own records, consumes part of your 10-lookup budget.
Exceeding the Limit Fails SPF Entirely, Not Partially
Once the lookup limit is exceeded, receiving servers treat the SPF check as a permanent error, effectively failing authentication for the domain regardless of whether the actual sending source was legitimate.
Flattening or Consolidating Includes Is the Common Fix
Reducing the number of nested includes, or using an SPF flattening service that resolves includes into static IP lists, keeps the lookup count within the required limit.
Next step: Use the Find DNS Records to check exactly how many DNS lookups your current SPF record triggers before you risk exceeding the limit.