About

This is a professional-grade diagnostic instrument designed for System Administrators, DevOps Engineers, and Email Marketers. Unlike standard tools that cache results or rely on slow backend processing, this application executes a Distributed Real-Time Scan directly from your browser using DNS-over-HTTPS (DoH). This ensures you see the exact status of an IP address as it propagates across the global DNS network.

We check against a comprehensive matrix of over 75+ databases, including Tier-1 providers (Spamhaus, SpamCop) and specialized lists (UCEProtect, SORBS). The tool analyzes return codes to distinguish between Policy Listings (e.g., dynamic residential ranges), Exploit Listings (e.g., infected nodes), and Reputation Listings (e.g., spam history).

Formulas

The core mechanism utilizes the reverse-octet DNS query standard. For an IPv4 address a.b.c.d being checked against a blacklist zone Z, the query structure is defined as:

DNS_A_Query(d.c.b.a.Z) →

{

127.0.0.x if ListedNXDOMAIN if Clean

We interpret the resulting bitmask or octet to categorize the listing type automatically.

Reference Data

Standard Return Code	Classification	Action Required
127.0.0.2	SBL (Spam Block List)	Direct evidence of unsolicited bulk email (UBE). Immediate audit of mail logs required.
127.0.0.3	CSS (Snowshoe)	Detected low-reputation IP range or "Snowshoe" spamming techniques.
127.0.0.4	XBL (Exploits)	Machine is likely infected with a botnet controller, proxy, or malware. Critical Security Risk.
127.0.0.10 to 127.0.0.11	PBL (Policy)	IP is part of a dynamic ISP pool (DHCP). Not allowed to run an SMTP server. Configure SMTP Auth via ISP.
NXDOMAIN	Clean	No listing found. The IP has a neutral or positive reputation in this zone.

Frequently Asked Questions

Not necessarily. Policy lists (like Spamhaus PBL) simply indicate that an IP belongs to a residential or dynamic range (DHCP) that should not be sending email directly. If you are a home user, this is normal. If you are running a dedicated mail server, your rDNS is likely misconfigured.

Propagation takes time (TTL). Furthermore, some lists (like SORBS or UCEProtect) have specific "aging" periods where an IP must be quiet for 48 hours to 7 days before automatic removal. Others require manual delisting requests via their website.

Our algorithm weighs the impact of specific lists. A listing on a Tier-1 provider (e.g., Spamhaus) penalizes the score significantly more than a listing on a niche or aggressive list (e.g., UCEProtect Level 3). A score below 80 suggests a high probability of emails landing in Junk folders.

Yes. The tool will first resolve the Domain's A-Record (primary IP) via DNS and then scan that IP. Note that this checks the reputation of the *hosting server*, not the domain name itself (URIBL).