What domain blocklists (DBLs/RHSBLs) should I monitor?
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You might have a clean sending IP and still find your emails getting blocked. That's domain blocklists (DBLs, sometimes called RHSBLs) at work. They don't care where your email is coming from. They care about your domain identity, and once your domain is flagged, it follows you everywhere.
Here's a quick breakdown of the ones that actually matter.
High-impact domain blocklists
| List | Query zone | Why it matters |
|---|---|---|
| Spamhaus DBL | dbl.spamhaus.org | Industry standard. Used by most major filters worldwide. |
| SURBL | multi.surbl.org | Checks URLs found inside your message body. |
| URIBL | multi.uribl.com | Deeply integrated with SpamAssassin. Flags URIs in content. |
| ivmURI (Invaluement) | uribl.invaluement.com | Catches more sophisticated spam patterns that slip past others. |
Medium-impact domain blocklists worth watching
| List | Query zone | Notes |
|---|---|---|
| SEM URI | uribl.spameatingmonkey.net | URI-focused checking |
| SEM FRESH | fresh.spameatingmonkey.net | Targets newly registered domains (a common spam signal) |
| Nordspam DBL | dbl.nordspam.com | Relevant if you send into Nordic markets |
| SORBS RHSBL | rhsbl.sorbs.net | Domain reputation, lower coverage than Spamhaus |
What domain blocklists actually check
It's not just your From address. DBLs scan several places in your email at once:
- Your From address domain
- Your HELO/EHLO domain (the domain your mail server announces itself with)
- Your Reply-To domain (if different from From)
- Every URL in your message body
- Domains referenced in message headers
That last one is worth pausing on. Even if your sending domain is clean, a single flagged link in your body can get the whole message blocked. This is why using third-party redirect services or link shorteners without vetting them first is a real risk (not just a theoretical one).
Why domain reputation outlasts IP reputation
IPs change. You can switch ESPs, move to a new IP range, or warm up a fresh address. Your domain is a fixed identity that accumulates its own history. Shared IP senders especially feel this, because the IP they send from belongs to their ESP, but the domain is all theirs. That's both the risk and the reason domain blocklists hit so hard.
Want to check if your domain is already listed anywhere? Run it through our free blocklist checker and see where you stand. If something looks off and you're not sure what to do next, the SOS hotline is free.
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