Postfix. Client host rejected: cannot find your hostname 1

[olegarr]

Hi all,

I have a problem and hope that somebody will help me.

We are running Postfix and everything is fine except that some clients of ours cannot send emails to us.

This is the information from var/log/maillog:

Jun 27 09:34:19 nico postfix/smtpd[12873]: reject: RCPT from
unknown[208.63.55.118]: 450 Client host rejected: cannot find your hostname, [208.63.55.118]; from=<SomeUser@boehmtvl.com> to=<oaronov@trondent.com>

In the postfix configuration I have:

postconf -e smtpd_helo_restrictions=&quot;permit_mynetworks,
reject_invalid_hostname, reject_unknown_hostname, reject_non_fqdn_hostname, reject_maps_rbl&quot;

I think that if I will remove &quot;reject_unknown_hostname&quot; they will be able to sent emails to us, but I do not want to open any holes for spammers.

So, my questions are as follows:

1. Why are they unable to send email to us?
2. Is it possible to change or edit something in Postfix configuration to allow emails from that domain (or from that IP) to come through even if DNS check will fail? If it possible, then how, where, and what should I change?

Please help me to resolve this puzzle.

Best regards and thank you very much in advance.
Oleg Aronov

 

[usige]

Oleg,
You are correct that the &quot;reject_unknown_hostname&quot; parm is causing Postfix to reject the mail. You can allow it by doing the following:

add the following to your smtpd_helo_restrictions parm after permit_mynetworks.

check_helo_access hash:/etc/postfix/ok-ips

In the file /etc/postfix/ok-ips put a line like:

208.63.55.118 OK

Create the hash:

postmap hash:/etc/postfix/ok-ips

reload postfix

It is important that the &quot;check_helo_access ...&quot; comes before &quot;reject_unknown_hostname&quot; since postfix traverses the list in order. Any way I hope that helps.

 

[olegarr]

Usige,

Thank you very much for your help. I will try to do it on Monday.

Best regards,
Oleg