mailcow-dockerized-docs/docs/u_e-why_unbound.md

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2017-05-06 00:22:26 +02:00
For DNS blacklist lookups and DNSSEC.
Most systems use either a public or a local caching DNS resolver.
2017-05-09 19:21:51 +02:00
That's a very bad idea when it comes to filter spam using DNS-based black hole lists (DNSBL) or similar technics.
2017-05-06 00:22:26 +02:00
Most if not all providers apply a rate limit based on the DNS resolver that is used to query their service.
Using a public resolver like Googles 4x8, OpenDNS or any other shared DNS resolver like your ISPs will hit that limit very soon.