Glossary
What is Blocklist (DNSBL)
Definition
A blocklist (DNSBL) is a database of IP addresses and domains with bad reputation that mail servers query to decide whether to block a message. Being listed on a major one (Spamhaus, Barracuda) sharply hurts deliverability.
You can check an IP or domain with a reverse DNS lookup against the list’s zone. Listings come from spam complaints, hitting traps, or compromise. Delisting is done via the list operator’s form after fixing the cause.
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