How are IPs or domains added to blocklists?

Blocklist additions occur through multiple detection mechanisms, each designed to identify different types of spam sources.

Spamtrap networks are a primary detection method. When mail arrives at addresses that exist solely to catch spam, the sending IP or domain gets listed. Pristine traps trigger immediate severe listings.

User reports feed into systems like SpamCop. When enough users report mail from a source as spam, that source gets listed. Volume and pattern matter more than individual reports.

Automated detection identifies characteristics associated with spam: open relays, compromised systems, botnets, and high-volume spam campaigns. These systems detect problems without requiring complaints.

Manual review adds persistent spammers and sophisticated operations that evade automated detection. Human analysts investigate reported campaigns and make listing decisions.

Multiple watchmen guard the harbor. Some watch for specific signals; others investigate suspicious activity.