Blocklists (Spamhaus, SpamCop, Barracuda, and others) publish IPs and domains observed sending spam. Receivers query them at connection time to reject or filter mail.
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.
Why does email blocklists matter for deliverability?
A Spamhaus SBL or DBL listing can block delivery to a large share of the internet within hours.
What is the first step to get started with email blocklists?
Check your IPs and domains against major blocklists weekly.
What is the most common email blocklists mistake?
Requesting delisting before fixing the cause; repeat listings become harder to remove.