On Mar 13, 2007, at 8:17 PM, jekillen wrote:

On Mar 12, 2007, at 5:14 PM, RW wrote:

Just as long as you understand the distinction between forward and
reverse DNS. Based on the whois record for for your IP address, at the
moment you appear to have the following reverse DNS for the address
range -

$ for i in `jot  8 224` ; do dig +short -x 75.7.236.$i  ; done

OK, It appears that it is the ISPs name servers who
are responding. When I call up my sights I get to the
machines they are on according to my present
DNS setup.

But that is what the public sees. If (which I strongly doubt) your own internal nameservers give a different result to

$ dig +short -x

then it still makes no difference to the rest of the world which, when doing a *reverse* lookup on your IP address doesn't get anything that looks like your domain name.

try www.brushandbard.com

That's not the question. RW was (correctly) talking about *reverse* DNS, aka DNS PTR records. That is we are looking at the translation *from* number *to* name.

If you look up one of my statically IP addresses

$  dig +short -x

you get that instead of


It took me many unpleasant hours on the phone to Verizon to get the reverse look up the way it is now. I spent those hours on the phone specifically because I did want to run my own direct to MX mailserver.

My mailserver sends out mail as being from lists.shepard-families.org (in the envelope and header froms) but identifies itself as gecko.ewd.goldmark.org

a regular look up of either of those returns

A reverse of that turns up


which when you do a regular lookup gets you

So my machine is claiming to be in goldmark.org, and doing a reverse lookup on its IP address points you back to goldmark.org. So that strongly suggests that when it identifies itself as goldmark.org, it is doing so with the consent not only of the person who controls the goldmark.org domain, but also with the consent of the person (in this case Verizon) who controls the IP address of the machine.

If mail from my machine failed this IP --> name1 --> IP --> name2 --> IP test (the test being that name1 and name2 are in the same domain and that "IP" is the same IP throughout), then mail from my machine would get a high spam score by most systems.

I really don't want to sound harsh with this, but if you aren't fully clear on concepts like reverse and forward DNS and authoritative servers for each, you really should be looking for a solution that doesn't involve you running a direct to MX system. You can still run your own mailserver which you can integrate with your webserver, but have it relay all of the outgoing mail to your ISP's SMTP host which is set up for the purpose.

Also if you post your queries to the postfix mailing list (I think I recall that you were using postfix) you will probably find lots of pointers to information explaining about configuration. "The Book of Postfix" (ISBN 1-59327-001-1) has a good discussion of the need for other hosts being able to reverse resolve the IP of your mail hub.


Jeffrey Goldberg                        http://www.goldmark.org/jeff/

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