A Recursive Loop in Sender Policy Framework (SPF) occurs when the domain owner’s SPF record includes a mechanism that includes itself, resulting in an infinite loop. This can cause SPF lookups to fail, which can impact email deliverability causing emails to be rejected or marked as spam.
To avoid a recursive loop, domain owners should ensure that their SPF record doesn’t include mechanisms that reference themselves. Instead, they should use mechanisms that point to specific domains or IP addresses that are authorized to send email on their behalf.
Additionally, domain owners should pay close attention to the number of DNS lookups their SPF record requires. An SPF record cannot include more than 10 DNS lookups, so it is important to keep the number of mechanisms to a minimum. You should not include your own domain in your SPF record. This can create a recursive loop, as the domain will try to look up its own SPF record, resulting in an SPF lookup failure.
In summary, SPF Recursive Loop is a common issue with SPF records that can negatively affect email deliverability. Domain owners can avoid this issue by ensuring that their SPF record doesn’t include mechanisms that reference themselves and by minimizing the number of DNS lookups required by their SPF record.
Here is an example of a recursive loop:
v=spf1 include:_spf.example.com -all _spf.example.com SPF "v=spf1 include:example.com -all"
In this example, a lookup for
_spf.example.com would refer to
example.com, which in turn would again look up
_spf.example.com, and so on. Instead of using an include loop in the SPF record, it is better to use the IP addresses directly in the record or to create a separate SPF record for each domain and use a redirect mechanism to point to it. This will also help in reducing DNS lookups and improve email deliverability.
It is not recommended to set up an SPF record with recursive loops as it can cause performance issues and deliverability problems. Recursive loops occur when the mechanism specified in the SPF record refers back to the domain that is being checked. It is best to simplify the mechanism to avoid the loop.
To ensure optimal SPF record performance, you should periodically review and optimize your SPF record. This can involve consolidating multiple SPF records into a single record, removing unnecessary DNS lookups, and reducing the number of included domains. By carefully managing your SPF record, you can ensure that your emails are properly authenticated and avoid SPF Recursive Loops.