Email Infrastructure // Online

Email Blacklist Checker.

An email blacklist checker scans your sending IP address or domain against 50+ DNS-based blacklists to determine whether your emails are being blocked. If your IP appears on even one major blacklist like Spamhaus or Barracuda, your inbox placement rate can drop below 10%. This free tool queries all major DNSBLs in parallel, returns results in seconds, shows severity levels for each listing, and provides direct links to delist request forms. For domain lookups, it also resolves your MX records and checks the underlying mail server IPs automatically.

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How to Use

Get Started in 3 Steps

Step 01

Enter IP or Domain

Type an IPv4 address (e.g., 192.0.2.1) or domain name (e.g., example.com). The tool auto-detects the input type. IPv6 is not supported due to inconsistent DNSBL coverage.

Step 02

Run the Scan

Click "Check Blacklists" to scan against 50+ DNS-based blacklists in parallel. For domains, the tool also resolves MX records and checks the underlying mail server IPs.

Step 03

Review and Delist

See your overall CLEAN or LISTED status with a per-list breakdown. For any listings, click to expand delisting instructions and follow the direct links to each blacklist's removal form.

How It Works

Under the Hood

When you submit an IP address, the tool reverses the octets and queries each DNSBL zone via DNS-over-HTTPS (e.g., 1.2.0.192.zen.spamhaus.org). An A record response means the IP is listed; NXDOMAIN means it is clean.

For domain lookups, the tool runs two parallel checks: (A) querying domain-specific blacklists like Spamhaus DBL and SURBL directly, and (B) resolving the domain's MX records to find mail server IPs, then checking those IPs against all IP-based blacklists.

All 50+ DNSBL lookups run in parallel using Promise.allSettled with a 5-second per-query timeout and a 10-second overall budget. Lists that time out or return errors are marked as "unknown" rather than "clean" to avoid false negatives.

Lists marked as requiring registration (like some Spamhaus data feeds) are still queried, but access failures are treated as "unknown" rather than an error, since they may block public DNS resolvers.

FAQ

Frequently Asked Questions

What is an email blacklist and how does it affect deliverability?
An email blacklist (also called a DNSBL or RBL) is a real-time database of IP addresses and domains identified as sources of spam. When a mail server receives an incoming message, it queries these blacklists to decide whether to accept, flag, or reject the email. If your sending IP or domain is listed on even one major blacklist like Spamhaus or Barracuda, your deliverability rate can drop dramatically — sometimes below 10%. Blacklists are maintained by independent organizations that use spam traps, user reports, and automated detection to identify problem senders.
How do I check if my IP address is blacklisted?
Enter your mail server IP address into the checker above and click "Check Blacklists." The tool queries 50+ DNS-based blacklists (DNSBLs) in parallel using DNS-over-HTTPS and returns results within seconds. Each blacklist result shows one of three states: listed (your IP appears on that list), clean (not listed), or unknown (the blacklist did not respond in time). For domains, the tool also resolves your MX records and checks the underlying mail server IPs automatically.
What should I do if my IP is on a blacklist?
First, identify and fix the root cause — common reasons include compromised accounts sending spam, misconfigured mail servers acting as open relays, or shared hosting where another user sent spam. Then, submit a delisting request to each blacklist. Our tool provides direct links to delist request forms for each blacklist where your IP is listed. Most blacklists like SpamCop and Barracuda will remove your IP within 24-48 hours after you fix the issue. Spamhaus may require additional documentation. Some lists like UCEProtect Level 1 auto-expire after 7 days.
How long does it take to get delisted from a blacklist?
Delisting times vary significantly by provider. SpamCop listings typically expire automatically within 24 hours once spam stops. Barracuda processes manual removal requests within 12-24 hours. Spamhaus may take 1-3 days and requires demonstrating the issue is resolved. UCEProtect Level 1 auto-removes after 7 days with no new spam, but Level 2 and 3 can persist for weeks. In all cases, the first step is always fixing the underlying issue that caused the listing — requesting removal without fixing the problem will result in immediate re-listing.
What is the difference between IP-based and domain-based blacklists?
IP-based blacklists (like Spamhaus SBL/XBL, Barracuda, and SpamCop) track the IP addresses of mail servers that send spam. They are the most widely used type. Domain-based blacklists (like Spamhaus DBL, SURBL, and URIBL) track the domains found in spam message content, links, and sender addresses — regardless of which IP sends the email. This means changing your sending IP will not help if your domain is listed. Our checker tests both types: for domain lookups, it checks domain blacklists directly and also resolves your MX records to check mail server IPs against IP-based lists.
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