How Common is the SPF Problem?

How Common is the SPF Problem?

Sender Policy Framework or SPF is an email authentication protocol that protects domains from cyber attacks like spoofing, phishing and spam. It allows domain owners to specify which email servers are permitted to send emails from their domain(s). This way, it is able to detect emails sent by forged sender addresses.

Unfortunately, SPF has several built-in limits that many people are unaware of. It is no secret that properly implementing SPF is not an easy task to accomplish. Moreover, the SPF protocol is confined to detecting a forged sender claim in the email’s envelope, which is used when the email bounces back.

SPF’s most significant stumbling block is the domain lookup limit. If this limit is exceeded, emails will fail the SPF check even if they are authentic. Furthermore, SPF’s use of the Return-Path address, which is the primary method for mail servers to identify the source of an email irrespective of the human-readable ‘From’ address, creates a loophole that allows phishing attacks that authenticate correctly but have a forged ‘From’ address.

How Common is the SPF Problem?​

Listed below are some of the most common issues encountered with SPF:


  • DNS lookup limit exceeded
    A single SPF record can only have ten lookups. This indicates that your record can only produce a maximum of 10 domain references and if the record exceeds 10 lookups, the SPF will fail.
  • Multiple SPF records
    It is worth noting that each domain can only have one SPF entry. Recipient servers will reject all if your domain has more than one entry. As a result, the email SPF check will fail. To resolve or avoid this issue, either merge the entries into one or remove the entries that are no longer in use.
  • Improper syntax
    The SPF record must be syntactically correct. Each SPF record must start with ‘v=spf1’ and end with ‘~all’, ‘-all’, or ‘?all’. It should not have multiple ‘all’ or ‘v=spf1’ parts in the entry.

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