How to remove your IP from S5H

S5H is a small, spam-trap-driven IP blocklist run by System 5 Hosting. Here is what a listing means and how to clear it.

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What it is

The list, in plain terms.

S5H is a public DNS blocklist published in the zone all.s5h.net and run by System 5 Hosting (S5H). It lists IP addresses, not domains, and covers both IPv4 and IPv6. The operator describes it as RFC 5782 compliant and says it is funded privately.

The list is built from spam traps: addresses the operator monitors that should never receive legitimate mail. An IP that sends to one of those addresses is added, so a listing points to your sending server, not the domain in your message.

S5H is a smaller list than the major blocklists and is not consulted by every receiver, but some mail servers do query it. If your mail is being deferred or rejected with a reference to all.s5h.net, the listing is worth clearing.

Why you get listed

What a listing on S5H means.

Mail to a spam trap Your IP sent a message to one of the addresses the operator monitors. Those addresses are not real mailboxes, so any mail reaching them is treated as spam and the sending IP is listed.

A compromised or abused host An infected machine, an open relay, or a hijacked account on the IP can send spam to a trap without your knowledge. The listing flags the behaviour of the IP, not a deliberate decision by you.

Poor sending hygiene Sending to stale, purchased, or scraped lists raises the chance of hitting a trap address. Repeated trap hits are what get an IP added and what get it re-added after removal.

How to get removed

Delisting, in order.

Removal is free. Fix the cause first — a listing you clear without a fix comes straight back.

1 Confirm the listing. Query all.s5h.net for your reversed IP, or use any DNSBL lookup tool. A positive DNS answer means the IP is listed; an empty answer means it is not, and there is nothing to remove.
2 Fix the cause first. Find and stop the spam source before you request removal: clean the infected host, close any open relay, secure the compromised account, and remove trap addresses from your lists. A removal request will not hold if the abuse is still active.
3 Self-delist from the listed IP. Visit usenix.org.uk/content/rblremove from the offending IP address itself. The operator says that if you request removal from that IP, you are delisted immediately. You can also trigger it with curl or telnet from the listed host. Do not exceed three requests per IP per day, as that can trigger further blocking.
4 Use the manual form if you cannot reach the IP. If you cannot browse from the listed address, submit the removal assistance form at usenix.org.uk/content/rblremovehelp with the listed IP and proof that you have resolved the security problem. The operator states an approved manual request is actioned within about 30 minutes.
5 Re-check before resuming. The zone uses a very short DNS TTL (five seconds), so removal propagates quickly. Re-query all.s5h.net to confirm the IP is no longer listed before you ramp your sending back up.

The official route

Straight to the source.

Removal happens on S5H's own tool — never through a paid service.

S5H removal tool ↗

How long it takes

Self-service removal from the listed IP takes effect immediately, and the five-second DNS TTL means it propagates within moments. Manual removals through the assistance form are actioned within about 30 minutes once approved. If the underlying spam source is still active, the IP will be relisted the next time it hits a trap.

Common questions

About S5H, specifically.

Does S5H charge to remove my IP? No. Removal is free through both the automatic self-service page and the manual assistance form. Any service offering to remove an S5H listing for a fee is a scam. The operator does accept voluntary donations, but these are not required and do not affect delisting.

How do I remove my IP from all.s5h.net? Visit usenix.org.uk/content/rblremove from the listed IP address itself and the operator delists you immediately. If you cannot browse from that IP, use the manual assistance form at usenix.org.uk/content/rblremovehelp with proof the problem is fixed.

Why does removal have to come from the listed IP? The self-service system delists whichever IP the request arrives from, so it has to see traffic from the offending address to know what to remove. If you are behind NAT or cannot reach the web from that IP, use the manual assistance form instead.

Why was my IP listed if I never sent spam? S5H lists any IP that sends to its spam-trap addresses. That often means a compromised account, an open relay, or malware on a host is sending without your knowledge. Investigate the machine and your outbound mail before delisting, or it will be listed again.

How long does S5H removal take? Self-service removal is immediate and propagates within seconds because the zone uses a five-second TTL. Manual requests through the assistance form are actioned within about 30 minutes once approved.

I delisted but got listed again — why? The spam source was still active and hit a trap address again. Removal does not fix the cause. Clean the compromised host, stop the spam, and remove trap addresses from your lists before you request removal.

The bounce behind the listing.

554 5.7.1 message rejected → The permanent bounce a listing most often triggers — what it means and how to clear it. 550 5.7.1 blocked → A rejection on reputation grounds — usually the same listing, seen from the sender side. Blacklist checker → Re-check your domain and every sending IP once the cause is fixed.

Do not fix it blind.

See every list you are on and every authentication problem behind the listing in one 40-second check — then let monitoring tell you the day a listing comes back.

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