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I setup a Linux server and run a command, host wan ip in terminal and it shows ... domain name pointer mail.domain.com.

How do i replace current new mail.domain.com to mail.newdomain.com?

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what are is the problem you are trying to solve? – umläute Oct 4 '13 at 12:09
Can you please add more details to your Q? It's difficult to understand what you're asking. – slm Oct 4 '13 at 13:20
up vote 1 down vote accepted

DNS works in both directions.

mostly it is used to map a human memorizable name (e.g. mail.domain.com) to IP-addresses (e.g. this is done via so-called A records, e.g.:

mail.domain.com. IN A

to change the IP-address that is resolved vrom mail.domain.com, you have to have control over the domain domain.com. only then you can change that record.

but it also works the other way round, to map IP-addresses to domain names. IP-addresses are (like domain-names) hierarchical in nature, but (unlike domain-names) the highest-level is on the left side. mapping works via PTR records, using a "pseudo-domain" in-addr.arpa a "reverse-lookup" record for the above example looks like the following (note the reverse ordering of the IP-address) IN PTR mail.domain.com.

to change the name that is resolved from the IP-address, you have to have control over the "domain" only then you can change that record.

so in order to change the reverse-lookup, you must find out who is in charge of your IP-range and request that they fix the PTR record.

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