kumomta/docs/reference/kumo.spf/check_host.md

kumo.spf.check_host

kumo.spf.check_host { PARAMS }

{{since('2024.11.08-d383b033')}}

This function will check SPF records from DNS for the given domain and IP address.

It takes three arguments:

• domain (string), the domain to check (for example, from the smtp_server_ehlo event)
• conn_meta (connectionmeta), used to get the client's IP address
• sender (optional string), the sender address to check

It will return an object containing the SPF disposition string and a result of type authenticationresult for use with msg:add_authentication_results().

The OPT_RESOLVER_NAME parameter {{since('2025.12.02-67ee9e96', inline=True)}} is an optional string parameter that specifies the name of a alternate resolver defined via kumo.dns.define_resolver. You can omit this parameter and the default resolver will be used.

Example: checking the SPF policy

kumo.on('smtp_server_ehlo', function(domain, conn_meta)
  -- Check the SPF policy for the domain and return the results.
  local result = kumo.spf.check_host(domain, conn_meta)
  print('spf', kumo.json_encode_pretty(result))
  if result.disposition ~= 'pass' then
    kumo.reject(420, 'go away')
  end
end)

might print something like this to the diagnostic log:

spf    [
  "disposition": "pass",
  {
    "result": "pass",
    "method": "spf",
    "reason": "matched 'all' directive",
    "method_version": null,
    "props": {}
  }
]

See Also:

• msg:add_authentication_results()