Local DNS server (for caching) is not configured on the server.
When a server has many incoming/outgoing emails that come through spam check by block lists, for example, URIBL it might abuse DNS public lookup provided by such services and get a block after certain amount of successful checks. After that, a corresponding warning appears in Plesk Email Security extension.
Resolution
Warning: Configuration of the local DNS server to cache requests is the tasks that has to be configured by a server administrator.
Configure local DNS server to decrease the load on public DNS servers and avoid blocks from URIBL side.
For example, systemd-resolved can be configured as described here: https://geekflare.com/linux-server-local-dns-caching/
Example steps for BIND DNS server shipped with Plesk:
Install the BIND DNS server component if it’s not yet: Log into Plesk > Tools & Settings > Updates > Add and Remove Product Components > BIND DNS server > Install Connect to the server via SSH. Run a check against the test point:
host -tTXT 2.0.0.127.multi.uribl.com
Usually, if caching is not enabled the response is:
2.0.0.127.multi.uribl.com descriptive text “127.0.0.1 → Query Refused. See ”http://uribl.com/refused.shtml»>http://uribl.com/refused.shtml for more information [Your DNS IP: 203.0.113.2]»
Run named-checkconf to check for syntax error in the configuration files:
named-checkconf
Add the local nameserver to the /etc/resolv.conf file:
vi /etc/resolv.conf
add to the top of the file:
nameserver 127.0.0.1
Restart BIND service (named-chroot for CentOS, bind9 is Ubuntu/Debian):
service named-chroot restart
Check that the service is running:
service named-chroot status
Wait a few minutes and then run the check against the endpoint again:
host -tTXT 2.0.0.127.multi.uribl.com This time the response should be: 2.0.0.127.multi.uribl.com descriptive text “permanent testpoint”
Note: If URIBL is not needed it might be simply disabled: