What does "too many DNS lookups" mean?

Receivers stop evaluating SPF after ten DNS-querying mechanisms and return permerror. Most treat that as a fail, so mail from a domain over the limit loses SPF entirely.

SPF checker

Validate SPF and count the DNS lookups before receivers do.

What this check does

Fetches the SPF record, expands every include, counts DNS lookups against the limit of ten, and flags syntax and policy problems.

Exactly one SPF record
Lookup count against the 10-lookup limit
Terminating all qualifier (-all, ~all, ?all, +all)
Deprecated ptr mechanism, syntax errors

Questions

What does "too many DNS lookups" mean?: Receivers stop evaluating SPF after ten DNS-querying mechanisms and return permerror. Most treat that as a fail, so mail from a domain over the limit loses SPF entirely.