How to Fix a Blacklisted IP — Reputation Recovery Guide (2025)
If your emails suddenly stop landing or start bouncing, there’s a good chance your sending IP is blacklisted. Blacklists (DNSBLs) flag IPs that look like spam sources — high bounces, spam complaints, compromised accounts, or careless list practices. The good news: you can fix this. The bad news: if you don’t remove the root cause, you’ll be relisted fast.
1️⃣ Confirm the Blacklist and Scope of Impact
Don’t guess — verify. Some providers ignore certain lists; others block instantly. Check where you stand and how bad it is.
Also send a test email to MailTested to see real-world results across filters, not just DNSBLs:
2. Find the Root Cause (Fix this first)
Delisting without a root-cause fix is useless. You’ll be relisted within days. Diagnose what actually triggered the listing:
a) Compromised credentials or server
- Out-of-pattern volume spikes, odd recipients, unusual sending times
- SMTP auth logs showing unknown IPs or mass submissions
Fix: rotate all SMTP/API keys, force password resets, patch MTA, enable rate limits and submission auth, block outbound on suspicious accounts until clean.
b) List hygiene failures
- High bounce rates, recycled spam traps, role accounts scraped online
Fix: remove hard bounces immediately, suppress unengaged 90+ days, validate new signups, ban purchased lists.
c) Shared IP contamination
If you’re on a shared node, a neighbor can poison the IP’s reputation.
Fix: move to a dedicated IP/subnet or isolate traffic by domain; enforce per-user rate limits.
d) Missing authentication or reverse DNS
Failed SPF/DKIM or no PTR/hostname alignment pushes providers to distrust your traffic.
Fix: set valid PTR to your mail host, ensure HELO/EHLO matches, and pass SPF/DKIM/DMARC on MailTested.
3. Stabilize the Traffic Before You Ask for Delist
- Pause bulk campaigns; allow only transactional and internal test mail
- Cut list size to engaged recipients only
- Fix authentication: SPF, DKIM, DMARC must all pass
4. Request Delisting — Do It Right
Each DNSBL has its own process, but the logic is the same: demonstrate control and remediation. When you submit a request, include:
- What happened (compromised account, list hygiene failure, shared IP abuse)
- What you changed (password resets, rate limits, removed sources, authentication fixes)
- How you’ll prevent it (engagement thresholds, bounce handling, monitoring cadence)
Keep it concise and factual. Most lists delist quickly if your house is actually in order.
5. If Delist Is Refused
- Re-audit logs; look for residual spam bursts or unauthorized traffic
- Tighten rate limits and outbound thresholds
- Consider moving marketing traffic to a fresh dedicated IP (only after fully clean)
- Warm up the new IP slowly (see schedule below)
6. Warm-Up Schedule After Delisting or IP Change
Days 1–3: 100–200 emails/day to highly engaged users
Days 4–7: 300–800 emails/day; monitor bounces & complaints
Week 2: 1–2k/day; add segments gradually
Week 3+: Scale toward target volume if metrics stay cleanAny spike in complaints or bounces? Freeze volume, fix the segment, and resume when stable.
7. Hardening Checklist (Prevention)
- Pass SPF, DKIM, DMARC on every domain and subdomain
- Use strict alignment (
aspf=s,adkim=s) once stable - Set proper PTR and ensure HELO/EHLO matches your mail host
- Apply per-user rate limiting and outbound anomaly alerts
- Remove hard bounces immediately; sunset inactive 60–90 days
- Segment by engagement; send re-engagement before suppression
- Rotate DKIM keys annually; audit SMTP users quarterly
8. Verify Headers to Prove the Fix
After changes, send a test and read the Authentication-Results line to confirm pass statuses.
Use MailTested’s header analyzer:
✅ Final Thoughts
A blacklist isn’t a death sentence — it’s a signal to tighten your operation. Fix the root cause, stabilize traffic, request delisting with evidence, and follow a conservative warm-up. Keep testing on MailTested to catch small problems before they become listings.