← Glossary
Reputation
What is Blacklist / blocklist (DNSBL)?
A published list of IPs or domains that receivers use to refuse or filter mail.
How it works in practice
Receivers query these lists over DNS during the SMTP conversation. Lists differ widely in who runs them and how seriously they're taken: a listing on a major one such as Spamhaus can block mail at many providers, while a minor list may affect almost nobody. Delisting needs the cause fixed first.
The common mistake
Requesting removal before fixing the cause, which gets the listing back within days.
Check it yourself
Related terms
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