Blocklist
01 Definition
Blocklist meaning: A published list of IPs or domains known for sending spam, used to filter mail.
A blocklist is a database of IP addresses or domains identified as sources of spam or abuse. Mailbox providers and filters check incoming mail against blocklists and may reject or spam-folder listed senders. Getting listed, often from spam trap hits or complaint spikes, can sharply cut deliverability until you fix the cause and request delisting.
Also called
Why it matters
How Blocklist fits the work
Being on a widely used blocklist can block much of your email at once, so monitoring the major lists helps you catch and fix reputation problems fast.
In context
After a spam trap hit, the sending IP appeared on a blocklist, and delivery to major providers dropped until the team requested delisting.
Practical note
Not all blocklists carry equal weight; being on a major one like Spamhaus hurts far more than a minor list, so prioritize which listings you rush to resolve.