A DNS-based Blackhole List (DNSBL) is a list of IP addresses known for sending spam or malicious traffic. Mail servers check these lists to filter incoming email.

My IP is listed – what should I do?

First, identify the cause (compromised server, open relay, spam activity). Fix the issue, then visit the blacklist’s website to request delisting. Most blacklists have automated removal after a waiting period.

Why are my emails being rejected?

If your sending IP is on a blacklist, receiving mail servers may reject your messages. Check your IP with this tool. Other causes include missing SPF/DKIM/DMARC records, sending from a shared IP with bad reputation, or sudden spikes in email volume.

How long does delisting take?

It varies by blacklist. Some (like Spamhaus) remove IPs automatically after 1-2 weeks if no further spam is detected. Others require a manual delisting request. Barracuda typically processes requests within 12 hours.

How do I prevent getting blacklisted?

Use proper email authentication (SPF, DKIM, DMARC), monitor sending reputation, avoid sudden volume spikes, keep your server secure (no open relays), and promptly handle abuse complaints. Regular monitoring with blacklist checks helps catch issues early.

All tools

Blacklist Check

Check if an IP address or domain is listed on DNS-based blacklists (DNSBL). Test against Spamhaus, Barracuda, SpamCop, and more.

Blacklist Results

Other DNS Tools

DNS Lookup

Query DNS records for any domain. Check A, AAAA, MX, CNAME, TXT, NS, SOA, SRV, CAA, and PTR records.

DNS Propagation Checker

Check if DNS changes have propagated across global DNS servers. Verify updates from Google, Cloudflare, OpenDNS, and more.

SPF / DKIM / DMARC

Generate SPF and DMARC records and validate SPF, DKIM, and DMARC. Improve email deliverability and protect against spoofing.

WHOIS Lookup

Look up domain registration information. Find registrar, creation date, expiry date, nameservers, and contact details.

SSL Certificate Checker

Inspect SSL/TLS certificates. Check issuer, validity dates, subject alternative names, and certificate chain.

DNS Health Check

Run a comprehensive DNS health check on your domain. Analyze nameservers, SOA, MX, web records, and email authentication.

Frequently Asked Questions

: A DNS-based Blackhole List (DNSBL) is a list of IP addresses known for sending spam or malicious traffic. Mail servers check these lists to filter incoming email.
: First, identify the cause (compromised server, open relay, spam activity). Fix the issue, then visit the blacklist’s website to request delisting. Most blacklists have automated removal after a waiting period.
: If your sending IP is on a blacklist, receiving mail servers may reject your messages. Check your IP with this tool. Other causes include missing SPF/DKIM/DMARC records, sending from a shared IP with bad reputation, or sudden spikes in email volume.
: It varies by blacklist. Some (like Spamhaus) remove IPs automatically after 1-2 weeks if no further spam is detected. Others require a manual delisting request. Barracuda typically processes requests within 12 hours.
: Use proper email authentication (SPF, DKIM, DMARC), monitor sending reputation, avoid sudden volume spikes, keep your server secure (no open relays), and promptly handle abuse complaints. Regular monitoring with blacklist checks helps catch issues early.

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