[Cialug] Email server

[David Champion]

Technically not always your ISP, although that is usually the case. You can
tell for sure by doing a "whois 8.8.8.8" (substitute your IP) and find out
who owns the netblock range that you fall into.

You can use "dig -x 8.8.8.8" to see what the current PTR is.

mxtoolbox has a bunch of nifty tools available for doing various dns
queries. This Arin lookup is nice:

https://mxtoolbox.com/arin.aspx

-dc


On Mon, May 1, 2017 at 2:26 PM, Nicolai <nicolai-cialug at chocolatine.org>
wrote:

> On Mon, May 01, 2017 at 12:53:59PM -0500, khamil8686 at gmail.com wrote:
>
> > One thing I wondered, if I set up an authoritative nameserver on port 53
> > using my domain name, point dns towards there, and put reverse lookup
> > for my home mail server, would emails be rejected?
>
> > Purely an academic example that I was curious about.
>
> Well, your authoritative nameserver wouldn't be responsible for
> answering reverse DNS queries for your IP address; that's your ISP's
> job.  In other words, nobody would ask your NS for the PTR record of
> e.g. 53.2.0.192.in-addr.arpa.  All those queries would go to your ISP's
> nameservers.
>
> dig +short ns cialug.org.
> dig +short cialug.org. # currently 67.224.64.36
> dig +short ns 64.224.67.in-addr.arpa.
>
> Nobody asks the cialug.org nameservers questions about 67.224.64.36.
>
> To get a specific PTR record for your IP address, you'd have to ask
> your VPS/colo provider.
>
> Nicolai
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