OT: Reverse Lookup Records for Mail Server

Billy A. Pumphrey bpumphrey at woodmclaw.com
Mon Oct 9 15:39:24 IST 2006

In the WIKI

The below is written.  I have known this to be a good practice for
sometime, but DNS gets a little confusing for me sometimes.  I apologize
for all of the OT that I do, but just searching the internet does not
give suggestions.  

Have a reverse lookup that matches your HELO/EHLO.
Many of these policies stem from the fact that spammers will forge
addresses. When you send mail to a system that doesn't know you, you've
become a potential spammer. You must show that you can be trusted before
you will be trusted, and one way of doing that is to have a reverse
lookup that matches what your system says it is. Unfortunately, this may
be a problem in virtual hosting situations. At the very least make sure
that your MX is listed in DNS as the name that will respond to the HELO.
See RFC 2821 for more information on the SMTP command HELO.

If the MailScanner machine is on the internal network, as in not in a
DMZ, and host name ends not in the domain name, how does one set it up?
Host names ends in host.domain.local.  

Does the host name just need to be changed to host.domaain.com?  That
would seemingly cause problems communicating with the internal machines,
or would it?

So if the host name is mailscanner.domain.com, Then the reverse dns
should be mailscanner.domain.com right?  Sounds right to me.  

What happens when the reverse DNS is mailscanner.domain.com but the
actual host name is mailscanner.domain.local?

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