Blacklist Checker

Check if an IP or domain appears on 19 known email blacklists (DNSBL).

What are Email Blacklists (DNSBL)?

DNSBLs (DNS-based Blackhole Lists) are databases that record IP addresses and domains known for sending spam or engaging in malicious activity. Mail servers worldwide check these lists in real time before accepting incoming email. If your IP is on one or more lists, your emails may be rejected or end up in spam.

Why might you end up on a blacklist?

Sending spam

The most common cause — either from the server itself, or from users in a shared hosting environment that the server hosts.

Compromised server

If your server has been hacked, attackers may be using it to send spam without your knowledge.

Shared hosting

In shared hosting, many sites share the same IP. If a neighbor sends spam, the shared IP gets blacklisted and affects everyone.

Incorrect PTR record

If the reverse DNS (PTR) record of your IP does not match the mail domain, some lists consider this suspicious and add the IP.

What does the Return Code mean?

When an IP appears in a DNSBL, the resolver returns an IP in the form 127.x.x.x. The last octet encodes the reason for listing. For example, 127.0.0.2 typically means spam source, 127.0.0.10 means policy violation. Each DNSBL has its own encoding scheme.

How to get removed from a blacklist

Step 1 — Identify the problem: Find out why you were listed. Check mail logs, scan for malware, confirm there is no open relay.
Step 2 — Fix the cause: Secure the server, remove malicious software, fix PTR/SPF/DMARC records.
Step 3 — Submit a delisting request: Each blacklist has its own process. Visit its website and fill in the delisting form.
Step 4 — Wait: Removal can take anywhere from a few hours to several days depending on the list.

Frequently Asked Questions

Does a blacklist affect email delivery?

Yes, significantly. If your IP is on the Spamhaus ZEN or another major list, many mail servers will reject your emails or send them directly to the spam folder. The impact depends on which list the recipient's server uses.

How long do you stay on a blacklist?

It depends on the list. Some lists, such as Spamhaus, remove automatically after a certain period if the malicious activity stops. Others, such as Barracuda, require a manual delisting request.

Does Έλεγχος Blacklist check a domain or an IP?

The Έλεγχος Blacklist accepts both. If you enter a domain, it first resolves the IP it points to and checks that. If you enter an IP directly, it checks the IP without a domain lookup.

What are SpamCop and Barracuda?

SpamCop is one of the oldest and most well-known DNSBLs — it is based on spam reports from users. Barracuda is a list maintained by Barracuda Networks, widely used by corporate mail systems. Being on these lists significantly affects email delivery.

📖 Read the full guide: Why Are My Emails Going to Spam? →