void lookup
A DNS query made during an SPF check that returns no answer (NXDOMAIN or an empty NODATA reply); receivers should allow at most two.
What it means
RFC 7208 calls a lookup void when it comes back with no records: either the name does not exist (NXDOMAIN) or it exists but has none of the type asked for. A record with includes for retired services, typing errors, or targets in domains that no longer exist produces void lookups. RFC 7208 adds the limit as a defence against records built to make receivers query names that do not exist.
The specification says receivers should stop after two void lookups and return permerror, and that two is the recommended default where the limit is configurable. This limit is separate from the ten-lookup cap, so a record well under ten queries can still fail on it.
Test each include and a or mx target in the record and remove the ones that resolve to nothing.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 7208: Sender Policy Framework (SPF), section 4.6.4rfc-editor.org
- RFC 7208: Sender Policy Framework (SPF), section 11.1rfc-editor.org
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