$TTL 24H
@       IN SOA  ns1.seudominio.com.br. email.seudominio.com.br. (
                                        0       ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
                IN      NS      ns1.seudominio.com.br.

100             IN      PTR     ns1.seudominio.com.br.
20              IN      PTR     mail.seudominio.com.br.
31              IN      PTR     webmail.seudominio.com.br.
254             IN      PTR     mx1.seudominio.com.br.