$SOA 21600 ns1.freeapp.net zone.surbl.org  1200 600 604800 21600
$NS 21600 a.surbl.org b.surbl.org c.surbl.org d.surbl.org e.surbl.org f.surbl.org g.surbl.org h.surbl.org i.surbl.org j.surbl.org k.surbl.org l.surbl.org m.surbl.org n.surbl.org