Blocklists (Spamhaus, SpamCop, Barracuda, and others) publish IPs and domains observed sending spam. Receivers query them at connection time to reject or filter mail.
What good looks like#
- Done: Check your IPs and domains against major blocklists weekly.
- Done: Identify the cause: compromised account, list purchase, spam trap hits, or a misconfigured forwarder.
- Done: Fix the root cause and document what changed.
- Done: Submit a delisting request through the blocklist's process with evidence of remediation.
- Done: Monitor for relisting for 30 days.
What bad looks like#
- Seen in audits: Requesting delisting before fixing the cause; repeat listings become harder to remove.
- Seen in audits: Ignoring minor blocklists that some corporate gateways still use.
How to move from bad to good#
Work through the good list in order and re-verify after each change. Most teams find one or two items from the bad list already present; fixing those usually produces the largest improvement.
Frequently asked questions#
How long does Spamhaus delisting take?
Often within hours for SBL and CSS if the cause is fixed. DBL domain listings can take longer.
Which blocklists matter most?
Spamhaus (SBL, XBL, DBL), SpamCop, Barracuda, and SURBL have the widest impact.