Should Reverse Lookup Match Exactly?

[Arlen Baker]

Hello -

Our ISP made some big changes (w/o any notice) to our IP's and since we are
running DNS on our server, this has caused all sorts of headaches. The
biggest is that we cannot send emails outside of our system anymore.

I believe that it is because the reverse DNS lookup does not match our
domain.

For example:
The reverse dns lookup on our IP address shows:
ip205-161-32-17-phx.jetstreamwireless.com

but our domain is fthinking.com.

Isn't this a problem? They said that it is NOT a problem, but I can't send
out any emails

Thanks for your help.

 

[Kevin D. Goodknecht [MVP]]

In

Hello -

Our ISP made some big changes (w/o any notice) to our IP's and since
we are running DNS on our server, this has caused all sorts of
headaches. The biggest is that we cannot send emails outside of our
system anymore.

I believe that it is because the reverse DNS lookup does not match our
domain.

For example:
The reverse dns lookup on our IP address shows:
ip205-161-32-17-phx.jetstreamwireless.com

but our domain is fthinking.com.

Isn't this a problem? They said that it is NOT a problem, but I
can't send out any emails

Thanks for your help.

You are saying that your DNS server is Authoritative for the public domain
now?
You will need to get them to delegate your IP Netblock to your DNS servers,
this should be no problem if you have a block of IPs. If you have only one
then have them create the proper reverse lookup or delegate the IP to you.
You will have to ask them what zone name you need to create. It is usually
delegated to you as the NetBlock ID.

 

[Unc]

-----Original Message-----
Hello -

Our ISP made some big changes (w/o any notice) to our IP's and since we are
running DNS on our server, this has caused all sorts of headaches. The
biggest is that we cannot send emails outside of our system anymore.

I believe that it is because the reverse DNS lookup does not match our
domain.

For example:
The reverse dns lookup on our IP address shows:
ip205-161-32-17-phx.jetstreamwireless.com

but our domain is fthinking.com.

Isn't this a problem? They said that it is NOT a problem, but I can't send
out any emails

Thanks for your help.


.

This is a huge problem.

First. make sure the server your SMTP gateway is running
on can properly communicate. Check IP address, default
gateway, etc. Do a ping of www.something.com and see if it
resolves properly. If it doesn't then there is your
answer.

If the ISP changed your company's public addy's then most
likely your external DNS server addy's are different.
Change the ip addy of the forwarding DNS server (i.e.
change the address of the ISP's primary DNS server in your
internal DNS servers forwarding list). Most likely this
will correct your issue.

Does your SMTP gateway have a log file? See if it gives
you any clues.

Also, from the SMTP server try to Telnet to another domain
on port 25 and send an e-mail manually. This can help you
determine the issue as well. (do a google for telnet
smtp 25 helo) etc.

Good luck

Unc

 

[Jonathan de Boyne Pollard]

AB> The reverse dns lookup on our IP address shows:
AB> ip205-161-32-17-phx.jetstreamwireless.com
AB> but our domain is fthinking.com.
AB>
AB> Isn't this a problem?

It is not.

AB> They said that it is NOT a problem, [...]

"They" are correct.

AB> but I can't send out any emails

Then _read the error messages_, that your mail system presents to you, to find
out what the problem with mail transport actually is. Stop floundering
around, and look at what the error actually is before trying to guess at its
cause.