Parallels Virtualization and Automation Software

RESOLUTION

Make sure that the name servers that are listed in /etc/resolv.conf have not been shut down and are working properly.

It's also very possible that the name servers in the /etc/resolv.conf file are working fine but the IP from where the client is accessing the server is not reverse resolvable. It can be checked with:

 

If you get 'not found' error, it is misconfiguration on the client's side, you can offer the client to contact his ISP to make the IP reverse resolvable. If you wish you could turn off the reverse lookup completely:

 

For Linux servers that uses 'xinetd' the -Rt0 option needs to be added to the beginning of the server_args line in the /etc/xinetd.d/smtp_psa file:

server_args = -Rt0 /var/qmail/bin/relaylock ....
 

It is necessary to restart xinetd then to apply the changes:

 

For Debian and FreeBSD  servers that uses 'inetd' instead of 'xinetd' the option is the same '-Rt0' but the modification must be made to the /etc/inetd.conf file:

smtp stream tcp nowait root /path/to/qmail/bin/tcp-env tcp-env -Rt0 ...

smtps stream tcp nowait root /path/to/qmail/bin/tcp-env tcp-env -Rt0 ...
 

It is necessary to restart inetd in order for the changes to take effect:

 

Note, /etc/inetd.conf may be overwritten and the options you added will be removed if you make certain changes through Plesk CP, for example add MAPS server.

Additional information

Option -Rt0 will be automatically added into /etc/xinetd.d/smtp_psa (/etc/inetd.conf on Debian and FreeBSD) in future version of Plesk Control Panel.