Mechanisms of the SPF record
Weronika Kapias avatar
Written by Weronika Kapias
Updated over a week ago

The "v" prefix

This prefix specifies the SPF version, in this case, "v=spf1," indicating version 1. It informs mail servers that an SPF record has been added for the domain and should be considered.

The “a”mechanism

This mechanism checks whether the IP address from which the email was sent belongs to the domain identified as the sender's domain.

The "mx" mechanism

Specifies which mail servers are authorized to send email on behalf of a certain domain.

The "include" mechanism

Informs mail servers to include a specific domain in the SPF configuration. This is useful when referring to the SPF policy of another domain, especially when using email services provided by an external provider.

The "all" mechanism

This is the last element in the SPF record and determines the default policy for email messages that do not match any of the previously defined mechanisms. There are three main options for the "all" mechanism:

  • "+all": All messages are automatically considered authorized, even if they don't match any of the earlier SPF mechanisms. This approach is not recommended as it significantly weakens the effectiveness of SPF.

  • "-all": All messages that do not match any of the earlier SPF mechanisms should be rejected. This is a restrictive approach.

  • "~all": Represents "soft fail," indicating that messages not matching any of the earlier mechanisms should be treated as suspicious but not rejected. This approach provides some flexibility and is less restrictive than "-all."

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