Every IP address has a "reputation". If your IP is associated with sending spam, hosting malware, or participating in DDoS attacks, it can end up on a Blacklist (RBL/DNSBL).
Why Your IP Reputation Matters
Major services like Gmail, Microsoft, and Cloudflare use reputation databases to decide whether to trust a connection. A bad score leads to:
- Emails going directly to spam.
- Constant "Are you a robot?" Captchas.
- Complete blockades from certain websites or APIs.
Common Blacklists
There are hundreds of lists, but some of the most influential include Spamhaus, Barracuda, and SORBS.
How to Fix a Bad Score
- Scan for Malware: Ensure no devices on your network are part of a botnet.
- Check DNS Records: If you run a mail server, ensure SPF, DKIM, and DMARC are perfect.
- De-listing Requests: Visit the blacklist provider's site and follow their "delist" process once you've fixed the underlying issue.