How to Check If IP Is Blacklisted

Online Blacklist Checkers

Free tools to check multiple RBLs:

https://mxtoolbox.com/blacklists.aspx
https://www.dnsbl.info
https://multirbl.valli.org
https://blacklistchecker.com

Command Line Blacklist Checks

IP="YOUR_SERVER_IP"
REV=$(echo $IP | awk -F. '{print $4"."$3"."$2"."$1}')

for RBL in zen.spamhaus.org bl.spamcop.net b.barracudacentral.org; do
  echo -n "$RBL: "
  dig +short $REV.$RBL
done

Email-Specific Checks

host -t A YOUR_DOMAIN

Monitor Continuously

#!/bin/bash
IP="YOUR_IP"

if dig +short $IP.zen.spamhaus.org | grep -q "127.0.0"; then
  echo "IP $IP is on Spamhaus" | mail -s "Blacklist Alert" admin@example.com
fi

Other Checks

• Email reputation: https://senderscore.org
• Google Safe Browsing: https://transparencyreport.google.com/safe-browsing/search
• VirusTotal: https://www.virustotal.com

Interpretation

• 127.0.0.2–127.0.0.11: spam reasons
• 127.0.0.3: CBL listing
• 127.0.0.4: compromised server
• No result: not listed

Few listings are normal; multiple listings indicate a serious issue.