warning: no MX host for nextra.sk has a valid A record

[BoOk]

>Nemate adsl? Me takhle kravi adsl modem.
>A co vam vrati prikaz "host -t mx nextra.sk" ?
>me vraci tohle:
>nextra.sk mail is handled by 100 mx-backup2.nextra.sk.
>nextra.sk mail is handled by 10 mailhub.nextra.sk.
>nextra.sk mail is handled by 95 mx-backup1.nextra.sk.

Nemam dsl som pripojeny vzduchom s verejnymi IPckami je to problem uplne
vsetkych domen domena nextrabol len priklad. host rozlisuje ok bezi mi tam
tam bind, ale sluzi iba ako autoritativny DNS server a dns pouzivam
providera vsetko resolvuje ok len postfix ktory pouzivam mi neviem poslat
postu kedze mi vyhodi hlasku ktoru som spominal 
warning: no MX host for domena.tld has a valid A record

BoOk