What is this
In the email deliverability scan we check the IP addresses of all your MX records against public DNS blocklists. Unlike reputation.dnsbl (primary IP only), this one walks every MX IP, IPv6 included.
Why it matters
A single tainted MX fallback wrecks deliverability anyway. Senders try MX records in order, so a listed second or third MX still routes part of your inbound and outbound mail through the bad path.
How to fix it
TransIP: Drop the problematic MXes. On Managed Mail, support assigns a clean IP pool. On your own VPS, request delisting at the relevant blocklist.
CloudFlare: Mail does not go through CloudFlare. Repoint your MX records to a clean mail provider, or fix the origin and request delisting yourself.
Strato or Antagonist: Ask support which IPs they assign for MX. If listed: ticket with proof and date, they handle delisting upstream.
Other: Stop outgoing bulk mail. Audit your mail flow for compromised accounts or open relays. Request delisting per blocklist. Wait 24-72 hours and retest.
Verify
The scan results page lists each MX IP and the blocklists that hit. Or do it yourself: dig MX yourdomain.com +short, reverse each IP, query <reversed>.zen.spamhaus.org.