bash script for mail related DNS lookups

check-domain.sh

#!/bin/sh

if [ "x" = "x$1" ]; then
	echo "usage: $0 <domain>"
	exit 1
fi

DOMAIN=$1

echo "Mail servers (MX)"
dig +short $DOMAIN MX

echo
echo "TXT records"
dig +short $DOMAIN TXT

echo
echo "Verifying DKIM"
for PREFIX in "google._domainkey" "smtpapi._domainkey"; do
    RES=$(dig +short $PREFIX.$DOMAIN TXT)
    echo "$PREFIX.$DOMAIN: $RES"
done

echo
echo "Verifying CNAME"
for PREFIX in "" "shop." "www." "members."; do
    RES=$(dig +short ${PREFIX}${DOMAIN} CNAME)
    echo "$PREFIX$DOMAIN: $RES"
done

echo
echo "Verifying DMARC"
RES=$(dig +short _dmarc.$DOMAIN TXT)
echo "_dmarc.$DOMAIN: $RES"