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ptr_host

local domain = kumo.dns.ptr_host(IP)
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.

Given an IP address in either V4 or V6 format as the input, returns the reversed address plus appropriate top level domain suitable for performing a reverse lookup.

This function is purely local string manipulation; no actual DNS queries are performed.

You will typically use lookup_ptr to perform an actual PTR lookup; this function is a utility function for the cases where you're doing something unusual.

print(kumo.dns.ptr_host '127.0.0.1')
-- prints out:
-- 1.0.0.127.in-addr.arpa

print(kumo.dns.ptr_host '::1')
-- prints out:
-- 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa