Free Email Blacklist Checker
Check if your email server IP or domain is listed on major email blacklists (DNSBLs). This tool scans against 12 popular blacklists including Spamhaus, Barracuda, SpamCop, and SORBS to help you diagnose email deliverability issues - all from your browser using DNS-over-HTTPS.
Understanding Email Blacklists
Email blacklists (also called DNSBLs or RBLs) are real-time databases of IP addresses that have been reported as sources of spam or malicious email. When a mail server receives an incoming connection, it can check the sender's IP against one or more blacklists to determine whether to accept, reject, or flag the message.
Blacklist lookups work by reversing the octets of the IP address and appending the blacklist's domain zone. For example, checking IP 1.2.3.4 against zen.spamhaus.org means querying 4.3.2.1.zen.spamhaus.org for an A record. If a record is returned (typically in the 127.0.0.x range), the IP is listed. The specific return code indicates the reason for the listing.
Being listed on even one major blacklist like Spamhaus can cause a significant portion of your outbound email to be rejected or sent to spam folders. Regular monitoring of your sending IPs is essential for maintaining good email deliverability. If you find yourself listed, address the root cause first (such as compromised accounts, open relays, or purchased email lists), then submit a delisting request to the blacklist operator.
Frequently Asked Questions
What is a DNSBL (DNS-based Blacklist)?
A DNSBL is a database of IP addresses published via DNS that are known to send spam or be associated with malicious activity. Mail servers query these lists in real time during the SMTP connection to decide whether to accept, reject, or flag incoming email. Popular DNSBLs include Spamhaus, Barracuda, and SpamCop.
How did my IP get blacklisted?
IPs typically get blacklisted for sending spam (even unintentionally), having an open relay or proxy, being part of a botnet, or sending mail from a dynamic/residential IP range. Sometimes a previous owner of the IP address caused the listing, and it carried over when you were assigned that IP.
How do I get delisted from a blacklist?
Each blacklist has its own delisting process. Most require you to visit their website, find the removal/delisting page, and submit a request. Before requesting removal, fix the underlying issue that caused the listing (stop sending spam, close open relays, patch compromised systems). Some lists like Spamhaus have a self-service removal tool, while others remove listings automatically after the offending behavior stops.
How long does delisting take?
Delisting timelines vary by provider. Some lists like the CBL remove listings automatically within 24 hours once the issue is resolved. Spamhaus self-service removals can be instant for first-time listings. Other lists may take 1-7 days to process removal requests. Repeat offenders may face longer waiting periods or manual review requirements.
What is the Spamhaus ZEN list?
Spamhaus ZEN is a combined lookup that checks three Spamhaus lists at once: SBL (Spamhaus Block List for verified spam sources), XBL (Exploits Block List for hijacked/compromised systems), and PBL (Policy Block List for dynamic/residential IPs that should not send mail directly). It is the single most widely used DNSBL in the world.
Does being on a blacklist always mean my emails will be blocked?
Not necessarily. Different mail servers use different combinations of blacklists, and many use blacklist data as just one factor in their spam filtering decision. Being listed on a major list like Spamhaus is very likely to cause delivery problems, while smaller or less widely used lists may have minimal impact. However, it is always best practice to resolve any blacklist listings promptly.