OpenVPN problems after migrating (4.7.1 Client host rejected: cannot find your hostname)

[syltrell]

Hello,

I have had openVPN set on our servers for years always working fine. Because we had Kloxo on CentOS 5 in our servers and became outdated besides having serious vulnerabilities, we decided to change to new servers with CentOS6 64 bits and Centos Webpanel.

After the migration in which we kept all the original IPs and all configs and files, we have now the problem that if a user of an email account hosted at the server tries to send an smtp mail (with thunderbird, opera, mailbird or other email client) through the openVPN installed at the same server, the mail is rejected with the message:

An error occurred while sending mail. The mail server responded:
4.7.1 Client host rejected: cannot find your hostname, [10.11.0.6].

It seems like if the email client connecting through the openVPN to the mail server, tries to resolve the outgoing IP with a reverse lookup of the hostname checking for a PTR record and an A record for the outgoing connection, but cannot find it because for the smtp client the outgoing IP appears as 10.10.10.6 (the subnet) and not the real IP where the openVPN is installed.

I don't know why when the email client looks for the outgoing IP address it gets the subnet address instead or if this is the problem, but was not happening before migration and config files were not changed.

As lateral information, kloxo was using qmail/courier and centos webpanel uses postfix/dovecot to handle the mail, don't know if it is relevant.

I also observed that when using an email account hosted outside the server for sending mails through the openVPN of the server, examining the headers of the received email it appear the subnet address and not the IP address where the openvpn is installed like appeared previous to the migration.

Before migration an email sent through that openVPN was showing:

Received: from [127.0.0.1] (name.hostname.com [111.222.333.111]

after migration an email sent from an outside account through the same openVPN shows in the headers:

Received: from [10.11.0.6] (unknown [10.11.0.6])


Can someone help me please? I have been one week already trying to figure this out and cannot find how to solve this issue. Thank you in advance.

Styrell

[syltrell]

Further information:

Sending smtp by port 587 works (although headers show the subnet as "Received from" instead of the host and the IP) but smtp by port 25 doesn't work :

An error occurred while sending mail. The mail server responded:
4.7.1 Client host rejected: cannot find your hostname, [10.11.0.6].

It seems something from Postfix...

[Bruce12]

Did you solve this ever? I don't see any replies.