[Solved] Postfix/smtp: Client host rejected: cannot find your reverse hostname

Hello,
few days ago I've installed ISPConfig on VPS. Wverything worked, but in mail queue i found some logs like this:
(host xx.xx.xx.xx[xx.xxx.xxx.xx] said: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [yyy.yyy.yy.yyy] (in reply to RCPT TO command))
or
(host mx.poczta.onet.pl[xxx.xxx.xxx.xxx] refused to talk to me: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [yyy.yyy.yy.yyy])

I've tried to found reason in Google, but I have not found a clear answer: Is it a postfix configuration or DNS / domain site wine?
And another question is how to fix it?

 

dig +short -t A your_hostname
dig +short -x IP_FROM_ABOVE
?

 

Problem solved. I forgot to set revDNS on VPS.

 

I'm sorry to reply to such an old topic But i'm having this error too.
tijmen@DESKTOP-GR6TGJ0:/mnt/c/Windows/System32$ dig +short -t A mail.domain.tld @8.8.8.8
213.x.x.x
tijmen@DESKTOP-GR6TGJ0:/mnt/c/Windows/System32$ dig +short -x 213.x.x.x @8.8.8.8
x.128/27.x.x.213.in-addr.arpa.
mail.domain.tld.

Don't they do follow ups on CNAMEs?

 

mail.domain.tld must be A-record. Reverse DNS is PTR-record, which can not be CNAME.

 

mail.domain.tld = a record as you can see by the DIG command i used
tijmen@DESKTOP-GR6TGJ0:/mnt/c/Windows/System32$ dig +short -t A mail.domain.tld @8.8.8.8
213.x.x.x
We dont have an actual PTR record in the zone of domain.tld but do have an authorative zone for
128/27.x..x.213.in-addr.arpa zone with and record for 140 being a PTR set to mail.domain.tld

 

In that case your error is not the same.

 

It is though. We are getting mails back that cannot be delivered because of the same error message. Does that mean that the receiving party is not doing recursive lookups?

 

Is the same error message you get really

What is the hostname for which the reverse can not be found?
Does

Code:

host 213.x.x.x

return the FQDN that your mail server sends mails as?

 

Did this from an external system:

ubuntu@dockers:~$ host 213.x.x.x
x.x.x.213.in-addr.arpa is an alias for x.128/27.x.x.213.in-addr.arpa.
x.128/27.x.x.213.in-addr.arpa domain name pointer mail.domain.tld

 

You did not answer:

 

You mean the real mail.domain.tld?

 

I mean, if you get the error message

and the PTR record exists for that IP-number, AND the return of reverse DNS matches the FQDN your mail server introduces itself to the other mail servers, then it should work. If, however, the receiving mail server tries to find some other hostname then mail server setup is faulty.
But maybe that construct where command host returns

Code:

x.x.x.213.in-addr.arpa is an alias for x.128/27.x.x.213.in-addr.arpa.
x.128/27.x.x.213.in-addr.arpa domain name pointer mail.domain.tld

is not suitable for mail servers. I do not recognize what that is. Seems to be CNAME for PTR records, which I find strange. How is that reverse record made in name service?
The PTR record should point to your mail server FQDN, that is mail.domain.tld.

 

We send an e-mail, that doesn't get delivered and we receive an e-mail containing that error message..

 

It's also not to every external domain. To google,hotmail etc it works just fine.