IP Blacklist (RBL/DNSBL) Checker Explainer
Not all blacklists are equal. Being on Spamhaus ZEN is reputation-killing; being on a no-name list usually isn't. This guide explains.
| RBL | Weight | Note |
|---|---|---|
| Spamhaus ZEN (sbl + xbl + pbl) | Critical | Most MBPs query Spamhaus ZEN directly. Listed = high spam-folder rate or outright reject. |
| Barracuda Reputation Block List (BRBL) | Major | Heavily weighted by mid-market MTAs (Exchange, on-prem). Removal via Barracuda Central. |
| SpamCop (bl.spamcop.net) | Moderate | Auto-lists on complaint volume; auto-delists after 24h of no complaints. Watch but don't panic. |
| SORBS | Low | Mostly residential / dynamic IP blocklist. Matters if you're on a VPS provider with a poor IP range. |
| UCEPROTECT (levels 1-3) | Minimal | Few major MBPs actually query it. Some hosting providers do. Removal is paid-only at higher levels, which is itself controversial. |
Lists the major RBLs (Spamhaus ZEN, Barracuda, SORBS, SpamCop, UCEPROTECT), their weight in inbox-placement decisions, and how to check.
Any deliverability investigation. Always check Spamhaus first.
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Articles, glossary entries, and other tools on the same topic.
You know the rule. See where you sit against it.
Reference pages tell you the benchmark. Outsolvi tells you whether your team is above or below it — per-rep, per-deal, per-week — and which behavior changes move the number. From $7/user/mo yearly.
See your numberNate built Outsolvi after watching every email-tracking tool he had ever used lie to him about opens. Outsolvi runs Tier 1 to 5 confidence scoring on every open, native in Outlook and Gmail, so the number on the dashboard is one a rep can actually act on.
We update these pages when the underlying mechanics change — new mailbox-provider rules, new tracker behavior, new measurement gaps. The dates above are real revisions, not auto-touches.