What it reads
The Spamhaus blocklist, for each IPv4 address of your mail servers.
Check 15 of 54 · Email authentication
Mail server reputation, explained.
Whether your mail servers sit on a spam blocklist. Shown to check by hand, never scored.
Engine 1.57.0, read 25 October 2026
Free checkAdviceReliability: Indicative
Can someone send email as you?
What the check does, and where it stops.
Why it matters
A listed mail server has its email refused. It is worth knowing, and worth confirming yourself.
What a finding looks like
What it finds is shown with a recommendation. It is advice, so it never lowers your score. If the check cannot finish, it is recorded as unknown: it carries no penalty, and it is never a pass.
Where its limits are
Blocklists refuse questions from cloud networks like ours, so we ask Spamhaus with a dedicated key, on the free check too. When your mail servers cannot be looked up, it says it could not check. We still never let this one change your score.
ReliabilityIndicative: a pointer, not a verdict
Check 15 is one of 16 in Email authentication. See it in its row on the scanner page, beside the rest of Email authentication.
See how your domain does.
The free check includes this one and takes about 30 seconds. No account. Nothing to install.