Why is the A record missing for sbl/xbl/pbl/dbl/zen.spamhaus.org?
Why is the A record missing for sbl/xbl/pbl/dbl/zen.spamhaus.org?
“I can’t trace zen.spamhaus.org, I get ‘host not found’…”
“All your DNSBLs are down! None of them resolve to an IP!”
“I can’t ping zen.spamhaus.org…”
The Spamhaus DNSBL zones (sbl.spamhaus.org, xbl.spamhaus.org, sbl-xbl.spamhaus.org, pbl.spamhaus.org, zen.spamhaus.org & dbl.spamhaus.org) are not hosts or servers, they are DNS zones.
- DNS zones map specially-formatted queries (such as ‘2.0.0.127.zen.spamhaus.org’) to DNSBL servers which in turn provide authoritative answers to the DNSBL queries.
- DNS zones do not normally have ‘A’ records, so a DNS zone can not resolve to an IP address or to a specific machine.
- Trying to resolve or ping a DNS zone is like trying to resolve or ping ‘.com’ (which is also a DNS zone) and ‘.com’ doesn’t have an ‘A’ record (so ‘.com’ cannot be resolved to an IP address either).
Each of Spamhaus’s DNSBL zones is load-balanced into sub-zones, served by over 80 DNSBL servers (‘mirrors’) located around the world. Our DNSBL server IP addresses change frequently as servers are added or removed from the pool, but the DNS zone always knows where to find them.
Never set an anti-spam filter to query the IP addresses of Spamhaus zone DNS servers, as these can change at any time. For IP address checks, always query only the advertized zones themselves: SBL, XBL, PBL, or preferably the combined Zen zone. For domains, use the DBL zone.
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