Short answer. First confirm which blacklist you are on via a DNS query to the DNSBL zone (for example Spamhaus ZEN). Then remove the root cause of the listing: a compromised account, an infected host, an open relay, or bulk sending without consent. Only then submit a delisting request on that specific list's site. Without fixing the cause, re-listing is inevitable.
What RBL and DNSBL are
RBL (Realtime Blackhole List) and DNSBL (DNS-based Blocklist) are databases of IP addresses and domains seen sending spam. Mail servers query them over DNS before accepting a message. If your IP is listed, the message is rejected or sent to spam.
Step 1. Confirm the listing
A DNSBL works with the "reversed" IP placed in a special zone. For IP 192.0.2.5 the query goes to 5.2.0.192.zone. A 127.0.0.x answer means listed.
dig +short 2.0.0.127.zen.spamhaus.org
# test answer 127.0.0.2 = "listed" (Spamhaus test record)
# Check real IP 192.0.2.5 against Spamhaus ZEN:
dig +short 5.2.0.192.zen.spamhaus.org
# Barracuda:
dig +short 5.2.0.192.b.barracudacentral.orgStep 2. Find the cause
- Compromised account — someone sends spam through your server.
- Infected host in the network — a bot spams from your IP range.
- Open relay — the server accepts and forwards third-party mail.
- Sending without consent — many "report spam" complaints.
- No SPF/DKIM/DMARC — lets attackers forge mail from your domain.
Submitting a delisting before fixing the cause is wasted effort: spam traps catch you again, and repeat requests are often processed slower.
Step 3. Fix the cause
- Rotate passwords, enable 2FA, review sending logs.
- Close any open relay, restrict SMTP authentication.
- Scan servers for malware.
- Configure SPF, DKIM and DMARC.
- Remove inactive addresses and anyone who never opted in.
Step 4. Submit a delisting request
| List | Check zone | Where to delist |
|---|---|---|
| Spamhaus ZEN | zen.spamhaus.org | Spamhaus Blocklist Removal Center |
| Barracuda | b.barracudacentral.org | Form on barracudacentral.org |
| SORBS | dnsbl.sorbs.net | SORBS support form |
| SpamCop | bl.spamcop.net | Auto-delist 24h after spam stops |
Many lists delist automatically once spam stops. You do not need to "beg" — just remove the source and wait out the cleanup window.
How enterno.io helps
enterno monitoring checks your mail domain and IP against blacklists and warns you if you get listed on an RBL — you find out before your recipients do. The /email-check tool shows whether SPF, DKIM and DMARC are set correctly, ruling out forgery as a listing cause. MX-lookup and SMTP-port availability monitoring confirm the mail server is up. enterno diagnoses and monitors — DNS records and delisting requests are submitted by the owner. Free plan: 10 monitors and 48+ tools, including a DNS check.
FAQ
How long does delisting take?
From a few hours to a few days. Automatic lists clear on a timer after spam stops; manual ones require a request and review.
Can I just change the IP?
Technically yes, but without fixing the cause the new IP will be listed too. Fix the spam source and authentication first.
Does a domain blacklist affect IP reputation?
Domain and IP are scored separately, but both affect deliverability. Check both the IP listing and the domain listing (DBL).
Check now: run a domain diagnosis at /email-check and set up blacklist monitoring. See also why emails go to spam.