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I am having problems sending email from a domain I host myself.

I have omitted the actual ip address in question, I am not sure how secure it is that I post it. However the problem is as follows:

According to my ISP the reverse was done for the my IP to point to the FQDN taht follows.


However I still get email undelivered:

host[] refused to talk to me: 550 Reverse DNS lookup failed for host

and upon testing I get the following error:

Reverse for points to an unknown host name (

The weirdest, perhaps, is that using some tools (i.e mxtoolbox) to check that the rDNS agrees to my SMTP banner, all checks fine, however, it fails when I use other tools.

What can be the error?

Do I need a reverse for every single domain I host or is it enough with the one for the mail server?


Ubuntu Server 10.04. LTS


Postfix version 2.x.x

Edit: In trying what you suggested I received the following:

first test

host -t a Using domain server: Name: Address: Aliases:

Host not found: 3(NXDOMAIN)

second test

host -t ptr

host -t ptr Using domain server: Name: Address: Aliases:

Host not found: 3(NXDOMAIN)

zone configuration

$TTL 12H

enter@  IN  SOA (
        1D )
            IN              NS    
            IN              NS    
            IN              MX      10
            IN              MX      20 IN A

www IN A IN TXT "v=spf1 a mx ip4: ip4: ~all"

localhost IN A

mail IN A
mail IN A
ns1 IN A
ns2 IN A
share|improve this question
In the configuration file that you posted there is no A record for neo001 – adamo Mar 14 '11 at 13:51

Try this:

host -t a

This queries Google's public DNS servers and asks them what the IP address for is. Now assuming the IP address is try this:

host -t ptr

Is the response ? If yes, then you have to wait a while for DNS caches to expire and read the new information. If not, then depending where the unexpected result appears, there exists a problem to be solved.

share|improve this answer
it did not seem to work – user74376 Mar 14 '11 at 11:18
Assuming the host in question is [I removed the server name], the first query failure means that the name does not exist, meaning that ns1 and ns2.[domain here].com are not configured to serve the A record for this name. Fix this first. – adamo Mar 14 '11 at 11:19
the A record seems fine where how can I post the sample file with the record? – user74376 Mar 14 '11 at 11:39
You posted the configuration file and there is no A record for neo001 – adamo Mar 14 '11 at 14:16
Either that, or similar to the www line. – adamo Mar 14 '11 at 20:59

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