About SORBS
SORBS (Spam and Open Relay Blocking System) is a long-running DNSBL operated since 2002, now under Proofpoint's stewardship after several ownership changes. It's actually a collection of sub-zones — SPAM (sending IPs reported for spam), HTTP/SOCKS/MISC (open proxies), SMTP (open relays), WEB (vulnerable web-hosted form-mail), DUHL (dynamic user host list, similar to Spamhaus PBL), ZOMBIE (compromised hosts), and ESCALATIONS (special-case listings). The aggregate zone dnsbl.sorbs.net queries them all.
Mid-market enterprise mail servers, many Postfix and Exim deployments with default DNSBL lists, and SpamAssassin scoring. SORBS is less universally used than Spamhaus or Barracuda but still appears in the DNSBL chains of a meaningful portion of receivers, particularly in Europe and APAC. Listed mail is typically soft-failed (spam folder) rather than rejected at SMTP, but receivers using strict DNSBL chains do reject.
Depends on the sub-zone: SPAM lists come from spamtrap hits and complaint reports; SMTP lists come from open-relay testing; HTTP/SOCKS/MISC come from open-proxy probes; WEB lists come from form-mail abuse detection; DUHL lists are pattern-based for dynamic/residential ranges; ZOMBIE lists are for malware-compromised hosts. Cold senders most commonly land on the SPAM sub-zone via spamtrap hits or aggregated complaint volume.
How To Get Delisted From SORBS
- 1
Look up the SORBS listing and identify the sub-zone
Go to https://www.sorbs.net/lookup.shtml and enter your IP. The result page shows which SORBS sub-zone(s) flagged you. Each sub-zone has a different removal path — the SPAM zone requires a paid-or-wait process (controversial, see below), while open-relay and proxy lists are self-clearing once the misconfiguration is fixed.
Note: SORBS lookup also references the listing reason in the response — check the details rather than treating all SORBS hits the same.
- 2
Fix the underlying issue before requesting removal
For open-relay or open-proxy listings: close the relay/proxy and verify with an external test. For DUHL (dynamic IP) listings: configure proper static rDNS matching forward DNS. For SPAM listings: terminate the sending campaign that triggered it, audit your lists for spamtraps, and reduce volume to receivers where you've seen low engagement.
Note: SORBS automated probes re-test for relay/proxy openness — if you request removal without actually closing the misconfiguration, you'll be re-listed instantly.
- 3
Submit a removal request via the SORBS portal
Create or log into a SORBS account at https://www.sorbs.net (account creation is free). Navigate to the Delisting section, submit your IP, and provide details about the corrective action. SORBS uses a ticket-based system — every request gets a ticket number you can reference.
Note: Account creation requires a valid email and is a prerequisite for any delisting request. Free webmail addresses are accepted but corporate emails get faster review.
- 4
Be aware of SORBS's controversial donation/payment angle
SORBS has historically offered an optional donation-based fast-track removal for SPAM-zone listings, with the standard wait being 6 months or longer for self-service expiration. This practice has drawn criticism from the anti-spam community — many ESPs and consultants recommend treating SORBS as a low-priority listing because of it. Proofpoint took over SORBS operation and the policies have evolved, but the practical reality is: SORBS removals are slow, and some delisting paths historically asked for donations.
Note: Many sophisticated receivers DO NOT use SORBS in their primary DNSBL chain precisely because of the historical payment practices. If you're only listed on SORBS and clean on Spamhaus and Barracuda, the practical deliverability impact is often small.
- 5
Wait for review and verify delisting
SORBS review times vary widely — same-day for open-relay/proxy fixes (the automated re-probe clears you fast), 1-2 weeks for SPAM-zone manual review, and historically up to 6 months for SPAM listings that don't go through the expedited path. Once delisted, run the lookup again to confirm and allow 24 hours for receiver-side cache propagation.
Note: SORBS listings without resolution can age out automatically over 3-6 months if no further offending activity is detected.
- 6
Decide whether SORBS is worth the effort
Pragmatic advice: if you're only listed on SORBS and clean on Spamhaus + Barracuda + SpamCop, the deliverability impact may not justify the SORBS removal hassle. Many cold-email operators treat SORBS as a 'monitor but don't urgently fix' listing. Focus delisting effort on Spamhaus and Barracuda, which have far larger receiver footprints.
Note: This is operator-specific judgment. If your sending vertical includes a lot of SORBS-using receivers, then SORBS matters more.
Operational Details
Open-relay/proxy lists: same-day to 24 hours via automated re-probe. SPAM sub-zone: 1-2 weeks under manual review, historically up to 6 months for low-effort paths. Automatic expiration: 3-6 months if no further offending activity.
Re-detection of the open relay, open proxy, or compromised host by SORBS probes; continued spamtrap hits; new complaints attributed to the IP. SORBS DUHL listings re-trigger if rDNS reverts to dynamic-looking patterns.
Lookup and ticket portal: https://www.sorbs.net. SORBS is now operated by Proofpoint — primary contact is through the ticket system.
SORBS And Cold Email
SORBS has a complicated reputation in the cold email community. The list itself is comprehensive and catches real spam infrastructure, but the historically slow removal process and the donation/payment angle on SPAM-zone delistings have led many sophisticated mail receivers to exclude SORBS from their DNSBL chain. Practically, a SORBS-only listing (clean on Spamhaus and Barracuda) often has limited deliverability impact — but if you also use shared infrastructure, you're at risk on multiple lists simultaneously. ColdRelay's dedicated infrastructure model removes the shared-IP risk that drives most cold-sender SORBS listings, and the per-mailbox 2-emails/day cap keeps the volume profile well below SORBS's spam-detection thresholds.
Frequently Asked Questions
How long does SORBS delisting take?
Open-relay and open-proxy listings clear same-day to 24 hours once the misconfiguration is fixed and SORBS's automated probe re-verifies. SPAM-zone listings are slower: 1-2 weeks under manual review, historically up to 6 months for low-effort delisting paths. Some operators wait for the automatic 3-6 month expiration instead of fighting through SORBS's removal process.
Does SORBS really charge for delisting?
Historically, SORBS offered an optional donation-based expedited removal for SPAM-zone listings, with the alternative being long manual-review wait times. This practice drew criticism and the policies have evolved under Proofpoint's stewardship. The current practical situation: removals are slow, the donation path may or may not still be active depending on listing type, and many anti-spam practitioners view SORBS with skepticism because of this history.
Should I prioritize SORBS removal if I'm also on Spamhaus?
No — fix Spamhaus first. Spamhaus is in the DNSBL chain of essentially every major receiver (Gmail, Microsoft 365, Yahoo). SORBS is in a much smaller subset. The deliverability ROI on Spamhaus delisting is dramatically higher. Address Spamhaus, then Barracuda, then SpamCop, then SORBS if time permits.
Why do some ESPs and consultants tell me to ignore SORBS?
Two reasons: (1) the historical donation/payment practices, which raised conflict-of-interest concerns, and (2) the relatively small receiver footprint compared to Spamhaus and Barracuda. Many sophisticated receivers have removed SORBS from their DNSBL chain over the years. That said, SORBS is still in the default config for many open-source mail servers, so it's not zero-impact — just lower-impact than Spamhaus.
Will SORBS listings expire automatically?
Yes, in most cases. SORBS listings typically age out over 3-6 months if no further offending activity is detected. For minor SORBS listings, waiting is often a reasonable strategy if you can't justify the manual-removal effort.
What's the difference between dnsbl.sorbs.net and the individual SORBS sub-zones?
dnsbl.sorbs.net is the aggregate query zone — a hit there means you're listed on at least one sub-zone. The individual zones (spam.dnsbl.sorbs.net, smtp.dnsbl.sorbs.net, web.dnsbl.sorbs.net, etc.) let receivers query a specific category. The lookup at sorbs.net shows which sub-zone(s) are flagging you, which determines the removal path.
Does ColdRelay's infrastructure prevent SORBS listings?
Yes for the structural risks: dedicated IPs on isolated Azure tenants remove the shared-infrastructure neighbour-effect, and the closed M365 outbound path eliminates open-relay and open-proxy listing causes by design. SORBS SPAM-zone listings tied to your own list hygiene (spamtraps, complaints) require sender-side discipline regardless of infrastructure — but the per-mailbox 2-emails/day cap keeps the volume profile far below SORBS's spam-trigger thresholds.