$ORIGIN 28.172.in-addr.arpa.
$TTL 5m

@ IN SOA dns.example. hostmaster.example. (1 0m 0m 0m 5m)

10.1 PTR moxacmepebble.mox1.example.
20.1 PTR moxmail2.mox2.example.
30.1 PTR dns.example.
40.1 PTR acmepebble.example.
50.1 PTR test.example.
60.1 PTR localserve.mox1.example.
70.1 PTR postfixmail.postfix.example.