IP Blocklist Checker (DNSBL)

Scan your IP against 38 blocklists including spam, malware, botnet, abuse, and policy databases to diagnose email delivery issues.

Enter a public IPv4 address to check against blocklists

38 Blocklists We Check

Spam Lists (25)

Spamhaus, Barracuda, SpamCop, SORBS, UCEPROTECT, SpamRATS, Mailspike, PSBL, Invaluement, and more

Malware Lists (7)

Spamhaus XBL/DROP, CBL, DroneBL, SORBS Zombie/Web, MSRBL Phishing

Policy Lists (3)

Spamhaus PBL, SpamRATS Dyna/NoPtr - dynamic IPs and missing rDNS

Abuse Lists (2)

BlockList.de, BACKSCATTERER - attack reports and backscatter sources

Reputation (2)

JunkEmailFilter, Lashback UBL - IP karma and suppression list abuse

Average scan time: 15-45 seconds depending on DNS response times

Understanding DNS-based Blocklists (DNSBL)

DNS-based Blackhole Lists (DNSBLs) are real-time databases of IP addresses known to send spam or engage in malicious email activities. Email servers worldwide query these blocklists to filter incoming mail, making them a critical component of email security infrastructure. If your IP is listed, your emails may be rejected or marked as spam.

Why IPs Get Blocklisted

IP addresses can end up on blocklists for various reasons: sending spam (intentionally or through compromised systems), hosting malware or phishing content, being part of a botnet, running an open mail relay, or having poor email authentication. Even legitimate senders can get listed if their server is misconfigured or compromised.

Impact on Email Deliverability

Being on a major blocklist like Spamhaus can severely impact your email deliverability. Recipients' mail servers may reject your emails outright, or they may end up in spam folders. This affects business communications, marketing campaigns, and even transactional emails like order confirmations and password resets.

Getting Delisted

Each blocklist has its own delisting process. Some automatically remove IPs after a period of good behavior, while others require manual requests. Before requesting removal, ensure you've addressed the underlying issue - whether it's removing malware, fixing a misconfigured server, or implementing proper email authentication. Most blocklist operators provide lookup tools and removal request forms on their websites.

Preventing Future Listings

Implement email authentication protocols (SPF, DKIM, DMARC), keep your systems secure and updated, monitor your sending reputation regularly, use double opt-in for mailing lists, and maintain clean email lists. Consider using dedicated IP addresses for high-volume sending and monitor bounce rates and spam complaints closely.

Understanding DNS-based Blocklists (DNSBL)

DNS-based Blackhole Lists (DNSBLs) are real-time databases of IP addresses known to send spam or engage in malicious email activities. Email servers worldwide query these blocklists to filter incoming mail, making them a critical component of email security infrastructure. If your IP is listed, your emails may be rejected or marked as spam.

Why IPs Get Blocklisted

IP addresses can end up on blocklists for various reasons: sending spam (intentionally or through compromised systems), hosting malware or phishing content, being part of a botnet, running an open mail relay, or having poor email authentication. Even legitimate senders can get listed if their server is misconfigured or compromised.

Impact on Email Deliverability

Being on a major blocklist like Spamhaus can severely impact your email deliverability. Recipients' mail servers may reject your emails outright, or they may end up in spam folders. This affects business communications, marketing campaigns, and even transactional emails like order confirmations and password resets.

Getting Delisted

Each blocklist has its own delisting process. Some automatically remove IPs after a period of good behavior, while others require manual requests. Before requesting removal, ensure you've addressed the underlying issue - whether it's removing malware, fixing a misconfigured server, or implementing proper email authentication. Most blocklist operators provide lookup tools and removal request forms on their websites.

Preventing Future Listings

Implement email authentication protocols (SPF, DKIM, DMARC), keep your systems secure and updated, monitor your sending reputation regularly, use double opt-in for mailing lists, and maintain clean email lists. Consider using dedicated IP addresses for high-volume sending and monitor bounce rates and spam complaints closely.