Você provavelmente quer algo assim. (consulte o link )
IN MX 1 ASPMX.L.GOOGLE.COM.
IN MX 5 ALT1.ASPMX.L.GOOGLE.COM.
IN MX 5 ALT2.ASPMX.L.GOOGLE.COM.
IN MX 10 ASPMX2.GOOGLEMAIL.COM.
IN MX 10 ASPMX3.GOOGLEMAIL.COM.
IN MX 10 ASPMX4.GOOGLEMAIL.COM.
IN MX 10 ASPMX5.GOOGLEMAIL.COM.
Certifique-se de adicionar o ponto final .