title: Mail domain health: DNSBL/RBL listings
agents: mail_domain_health
catalog: app/mail_domain_health
license: GPLv2
distribution:
description:
 This check queries a configurable set of DNS blacklists (DNSBLs) for the IP
 addresses of a mail server, collected by the {mail_domain_health} special agent.
 The target may be a host name (whose current A/AAAA addresses are all checked,
 keeping the service item stable across IP changes) or an IP literal.

 The number of listings is measured against configurable levels (default {WARN}
 at one, {CRIT} at two). Each IP is annotated with its reverse DNS (PTR) name,
 and every queried list is shown individually in the service details. Queries
 that are refused or blocked by a list operator (for example Spamhaus when
 queried through a public resolver) are distinguished from genuine "not listed"
 answers. Optionally a forward-confirmed reverse DNS (FCrDNS) check is reported
 per IP.

 All thresholds and states are configurable via the rule "Mail security:
 DNSBL/RBL listings".

item:
 The configured host name or IP address.

discovery:
 One service is created for each configured target and, when enabled, for the
 resolved MX hosts of each domain.
