#!/bin/sh
 set -euC
 
 # nfsn-dns-dmarc DOMAIN NAME EMAIL_NAME POLICY
 
 # nfsn-dns-dmarc "example.com" "" "" "none"
 # nfsn-dns-dmarc "example.com" "" "" "quarantine"
 # nfsn-dns-dmarc "example.com" "" "" "reject"
 
 # Arguments.
 
 domain="$1" ; shift
 name="$1" ; shift
 email_name="${1:-"postmaster"}" ; shift
 policy="$1" ; shift
 
 # Process.
 
 name="_dmarc${name:+".$name"}"
 data="$(
     printf "%s" \
         "v=DMARC1; " \
         "p=$policy; " \
         "sp=$policy; " \
         "pct=100; " \
         "rua=mailto:$email_name@$domain"
 )"
 
 # Update.
 
 nfsn-dns-update "$domain" "$name" "TXT" '' "$data"