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iprev

Since: Version 2025.12.02-67ee9e96

The functionality described in this section requires version 2025.12.02-67ee9e96 of KumoMTA, or a more recent version.

local mail_auth = require 'policy-extras.mail_auth'
local auth_result = mail_auth.iprev(IP)

The mail_auth.iprev function performs the iprev authentication method as specified by RFC8601 Section 3, and returns an AuthenticationResult representing the status of the check.

The IP parameter is a string representation of the IP address; for example, "127.0.0.1" for an IPv4 address of "::1" for an IPv6 address.

At most 10 of the PTR names are followed with forward A/AAAA lookups; names beyond that are ignored. RFC 8601 Section 3 requires such a limit and cites the value of 10 used by SPF.

See mail_auth.iprev_msg for a version of this check at accepts a Message object instead.