What Is SPF Flattening, And How Does It Work?

SPF too many DNS lookups error often leads to mail authentication failure and mails getting rejected. The SPF lookup mechanism allows up to 10 DNS lookups, beyond which there would be an SPF lookup failure. SPF flattening is one of the solutions that can avoid this error and ensure the emails’ deliverability.

spf too many dns lookups

Why Is SPF Flattening Relevant?

SPF flattening helps in avoiding the DNS lookup error significantly. It minimizes the chance of the emails getting flagged as spam since it becomes easier for the receiver to validate SPF.

Flattening causes SPF compression by doing away with various SPF mechanisms and finalizing it with a single SPF record containing all IP addresses related to multiple domains. Instead of using mechanisms that point to numerous domains that are to be included, they are represented directly by the IP addresses. Thus, it helps in avoiding errors like ‘Permerror SPF permanent error too many DNS lookups.’ The error usually shows up if the number of DNS lookups goes beyond the permissible SPF lookup limit of 10.

How Does SPF Flattening Work?

The SPF flattening technique is useful when the DNS lookup limit is approached due to an increased number of SPF mechanisms. Using the SPF flattening process, SPF mechanisms like ‘a,’ ‘mx,’ and ‘include’ are removed, which gives a simplified SPF record. It reduces the number of DNS lookups. Otherwise, the presence of each one of such mechanisms will unnecessarily add a lookup count.

Once the SPF record is flattened, the domains earlier pointed to by the mechanisms are represented solely by a string of ip4 and ip6 rules in a single SPF record. While the usual SPF record will need multiple DNS queries, the flattened one only needs one. SPF flattening’s prime motive is reducing the number of DNS queries, thus preventing email authentication failure.

Multiple SPF records and numerous DNS queries are among the common SPF errors. The SPF lookup counter has a limit set for ten, and beyond that, there will be an SPF lookup failure. However, SPF flattening is a useful and straightforward solution that can significantly solve the failure issue and help with successful email authentication.

multiple spf records

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