Email Blacklist

What is an Email Blacklist?

An email blacklist (also called a DNSBL — DNS-based Blackhole List, or RBL — Real-time Blackhole List) is a database of IP addresses and domains that have been identified as sources of spam or malicious email. Mail servers query these lists in real time to decide whether to accept, reject, or flag incoming messages.

Being listed on a major blacklist can cause your emails to be blocked or sent to spam across millions of inboxes. Even legitimate senders can end up blacklisted if their IP or domain is associated with spam activity — often due to compromised accounts, poor list hygiene, or shared hosting with spammers.

Major Email Blacklists

• Spamhaus — The most widely used blacklist. Includes SBL (manual listings), XBL (exploited hosts), and PBL (dynamic IP policy).
• SpamCop — Automated blacklist based on spam reports from users.
• Barracuda (BRBL) — Maintained by Barracuda Networks, used by many enterprise mail gateways.
• SORBS — Spam and Open Relay Blocking System.
• DroneBL — Tracks compromised hosts and DDoS participants.

How to Get Delisted

1. Identify which blacklist(s) you're on.
2. Fix the root cause (compromised account, bad list, open relay).
3. Request removal through the blacklist's delisting process.
4. Monitor to ensure you don't get relisted.