# IP blocklists

IP blocklists are databases of addresses reported for spam, attacks, malware or proxy use, published by anti-abuse organisations and security vendors and queried by websites, mail servers and fraud systems. An exit that appears on a relevant list is challenged or refused regardless of how it is used today. Providers of dedicated addresses screen inventory against these lists; on rotating pools the provider retires listed exits.


## Kinds of lists

- Spam and mail-abuse lists (DNSBLs), mostly relevant to port 25, which proxy networks block anyway.
- Proxy and VPN detection lists that flag hosting ranges and known gateway addresses.
- Threat-intelligence feeds built from attack telemetry, refreshed hourly.
- Site-specific denylists kept by a single target from its own experience.


## Checking an address

Several public lookup services aggregate the main lists; check a dedicated address when it starts drawing challenges, and ask for a replacement if it is listed through no fault of yours.


## How it works at ProxShift

ProxShift screens datacenter ranges for blocklist hits before they reach an order and replaces dedicated addresses that stay unusable; port 25 is blocked on every network so exits never earn mail-abuse listings.

Source: https://proxshift.com/glossary/blocklists