Reject clients with no reverse hostname

Arthur_Mino
Arthur_Mino used Ask the Experts™
on
G'day fellow postfix junkies!
I can get postfix to reverse name lookup IP addresses.

postfix "Reject clients with no reverse hostname" does not find reverse hostname for any IP address. I can check host names on IP address from the command line ok, but postfix doesn't seem to find any. Blocks all emails.
Linux CentOS.
I get the feeling postfix might need a missing setting on where to resolve hostnames to IP addresses.

Tearing my hair out!

Any Assistance much appreciated,

Cheers,

Arthur
450 4.7.1 Client host rejected: cannot find your reverse hostname, [209.85.217.226]  - this a mail-gx0-f226.google.com

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I think this has got to do with your sending address not being reverse mapped. try doing a
host your-ip-address

Author

Commented:
G'day Nabeelmoidu,

I have a registered reverse DNS name, it comes up ok. It looks like postfix needs DNS settings. I just don't get it.
Where does postfix get it's revers name look up from?

Cheers,

Arthur
It should be from the system's normal locations etc/hosts and the dns
can u give us a brief of your setup,
what's osx-server got to do here ?
are you trying to send mails from the server itself or a different client
what is your system hostname and what does the smtp_bind_address in master.cf point to?
what is the output of host command for that IP?
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Author

Commented:
G'day Nabeelmoidu,,

It should be from the system's normal locations etc/hosts and the dns
- The system does revers DNS searches fine, postfix does not want to resolve from those settings

can u give us a brief of your setup,
- Linux CentOS Postfix - simple, the SMTP log shows reverse DNS searches as connect from unknown[209.85.210.201]  when I run # host 209.85.210.201  I get
201.210.85.209.in-addr.arpa domain name pointer mail-yx0-f201.google.com. so the system reverses ok,

what's osx-server got to do here ?
- OS X Server runs postfix with the same result.

are you trying to send mails from the server itself or a different client
- Receive emails, I want to apply the postfix policy that emails trying to get in must come from a server that has a reverse dns registered

what is your system hostname and what does the smtp_bind_address in master.cf point to?
- not sure why these details are important, I don't wish to bind my smtp to any other smtp server. My smtp server reselved its own reverse dns fine.

what is the output of host command for that IP?
- host 209.85.210.201  I get
201.210.85.209.in-addr.arpa domain name pointer mail-yx0-f201.google.com. so the system reverses ok, it's only postfix that doesn't seem to do it.
President
Commented:
Hi,

> - Linux CentOS Postfix - simple, the SMTP log shows reverse DNS searches as connect from
> unknown[209.85.210.201]

It is definitely an issue with postfix. It can not resolve hostnames. the unknown shows that.  

Postfix in CentOS uses the system resolver : hosts and dns.

You nent to try to resolve names over the postfix host not over your client system to see if there's a problem over the postfix server.

Author

Commented:
G'day KeremE,

So you're saying that when you apply the Reverse DNS IP policy to postfix, postfix gets all it's DNS settings from the hosts and DNS etc files?

But why is that I can reverse resolve ip addresses from the command line but postfix can't seem to want to do it?

Cheers,

Arthur
Kerem ERSOYPresident

Commented:
Yeah postfix makes a query over the localsystem. In fact this is why we're all trying to nderstand why in the worlp postfix is acting differently than the command line resolver.

Will you post your hosts, nsswitch.conf and resolve.conf here? BTW all files are relative to the /etc directory.

Cheers,
K.
Kerem ERSOYPresident

Commented:
Can you confirm that when you issue the below command from the command line of your postfix server you get something similar to that :

$ nslookup 209.85.210.201

Server:         x.y.x.t
Address:        x.y.z.t#53

Non-authoritative answer:
201.210.85.209.in-addr.arpa     name = mail-yx0-f201.google.com.

Authoritative answers can be found from:
210.85.209.in-addr.arpa nameserver = ns4.google.com.
210.85.209.in-addr.arpa nameserver = ns1.google.com.
210.85.209.in-addr.arpa nameserver = ns2.google.com.
210.85.209.in-addr.arpa nameserver = ns3.google.com.
ns1.google.com  internet address = 216.239.32.10
ns2.google.com  internet address = 216.239.34.10
ns3.google.com  internet address = 216.239.36.10
ns4.google.com  internet address = 216.239.38.10

Also please post your main.cf too.

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