SharkDNS guide
4 min readIP blacklist check explained
Understand DNS-based blocklists, why an IP gets listed, and how to read listing reasons.
IP blacklist checkerRBL lookupDNSBLspam blacklist
When to use it
Check blocklists when outbound mail is rejected, after moving to a new server or IP range, or when monitoring the reputation of shared hosting infrastructure.
How DNSBL lookups work
The IP address is reversed and queried as a DNS name under each blocklist zone. A positive A record means the zone lists the IP, and the accompanying TXT record usually explains why.
How to interpret listings
Not every listing means abuse. Policy zones list dynamic or unassigned ranges by default. Check the reason string, confirm whether the zone affects your receivers, and follow the zone delisting process when needed.
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