Barry Margolin barmar at
Mon May 28 14:31:42 UTC 2012

In article <mailman.886.1338202161.63724.bind-users at>,
 "Amira Othman" <a.othman at> wrote:

> Hi all
> I configured bind9 on centos 5.8 server that has postfix mail server running
> on. When I added my ISP DNS ips to forwarders the mail server stopped
> sending mails and gives me DNS error'
> requires that all mail servers must have a PTR record with a valid Reverse
> DNS entry. Currently your mail server does not fill that requirement.

I don't believe that changing your forwarders could have caused this.  
This is the receiving server trying to do a reverse lookup of your IP, 
which should involve your authoritative DNS, but forwarders only affects 
caching DNS.

> But I didn't change mail server configuration and its MX record points to
> one of ISP DNS as I am still using their DNS. What's wrong on my
> configuration or what's missing?

This has nothing to do with MX records, which are used for your incoming 
mail.  The error is happening on outgoing mail, which uses your reverse 

> I also can't nslookup my DNS server although I added reverse zone in my
> zones. Should I have PTR in registrar also or it's just in my DNS server?

Your ISP needs to delegate the reverse DNS to your servers.  This should 
have been necessary all along.

Barry Margolin
Arlington, MA

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