请跟我说明一下DNS配置文件里的内容。

gkimcc

//
// named.conf for Red Hat caching-nameserver
//

options {
        directory "/var/named";
        dump-file "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        /*
         * If there is a firewall between you and nameservers you want
         * to talk to, you might need to uncomment the query-source
         * directive below.  Previous versions of BIND always asked
         * questions using port 53, but BIND 8.1 uses an unprivileged
         * port by default.
         */
         // query-source address * port 53;         
};

//
// a caching only nameserver config
//
controls {
        inet 127.0.0.1 allow { localhost; } keys { rndckey; };
};

zone "." IN {
        type hint;
        file "named.ca";
};

zone "localdomain" IN {
        type master;
        file "localdomain.zone";
        allow-update { none; };
};

zone "localhost" IN {
        type master;
        file "localhost.zone";
        allow-update { none; };
};

zone "0.0.127.in-addr.arpa" IN {
        type master;
        file "named.local";
        allow-update { none; };
};

zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa" IN {
        type master;
        file "named.ip6.local";
        allow-update { none; };
};

zone "255.in-addr.arpa" IN {
        type master;
        file "named.broadcast";
        allow-update { none; };
};

zone "0.in-addr.arpa" IN {
        type master;
        file "named.zero";
        allow-update { none; };
};

include "/etc/rndc.key";

我的DNS安装好后默认这样的配置，哪位高手跟我说明一下其中各段的意思？
哪里是 本机正向解释 ，哪里是 本机的反向解释
哪里是本地域的正向解释，哪里是本地域的反向解释
我准备配置邮件服务器，还要添加什么内容吗？

gkimcc

高手都上哪里去了？

gkimcc

顶到高手出来