Email Blacklist Removal: Step-by-Step Guide
Identify if your IP or domain is blacklisted, understand why it happened, and follow the delisting process for major blacklist providers.
What Are Email Blacklists?
Email blacklists (also called blocklists or DNSBLs) are databases of IP addresses and domains known to send spam. Mail servers check incoming email against these lists and reject or flag messages from listed senders.
Being blacklisted means your emails go straight to spam or are rejected outright. Even legitimate senders get blacklisted due to compromised servers, shared IP reputation, or accidental spam complaints.
Checking Blacklist Status
Before troubleshooting deliverability issues, check if your sending IP or domain is listed:
# Check your IP against major blacklists
# Using MXToolbox (web-based)
# https://mxtoolbox.com/blacklists.aspx
# Using command line (check Spamhaus)
dig +short 100.51.198.203.zen.spamhaus.org
# If listed: returns 127.0.0.x (where x indicates the list)
# If clean: returns NXDOMAIN (no result)
# Check Barracuda
dig +short 100.51.198.203.b.barracudacentral.org
# Check SpamCop
dig +short 100.51.198.203.bl.spamcop.net
The IP address is reversed in the query (203.198.51.100 becomes 100.51.198.203).
Major Blacklists and Their Impact
| Blacklist | Impact | Delisting Process |
|---|---|---|
| Spamhaus SBL | Very high (used by most mail servers) | Manual request, requires evidence of fix |
| Spamhaus XBL | High (compromised hosts) | Automatic after cleanup |
| Barracuda BRBL | High (enterprise mail filters) | Self-service web form |
| SpamCop | Medium (auto-expires after 24-48 hours) | Automatic expiry |
| SORBS | Medium | Self-service delisting |
| UCEPROTECT | Low-Medium | Automatic expiry (Level 1: 7 days) |
The Delisting Process
Step 1: Identify the Root Cause
Before requesting removal, fix the problem that caused the listing:
- Compromised server — Check for unauthorized SMTP relay. Review mail logs for suspicious outbound email.
- Spam complaints — Check feedback loops (FBLs). If users are marking your email as spam, fix your content or list practices.
- Shared IP — If you are on a shared server, another tenant's spam may have caused the listing. Consider a dedicated IP.
- Open relay — Ensure your mail server does not accept and forward mail from unauthenticated senders.
Step 2: Fix the Problem
# Check for unauthorized relay
grep "relay=" /var/log/mail.log | grep -v "relay=127.0.0.1"
# Check outbound email volume (unusually high = compromised)
grep "status=sent" /var/log/mail.log | wc -l
# Verify mail server is not an open relay
telnet your-server.com 25
EHLO test
MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>
# Should respond with "Relay access denied"
Step 3: Request Delisting
Each blacklist has its own process:
- Spamhaus — Visit
https://check.spamhaus.org/, enter your IP, follow the removal request form. Include details of what caused the issue and what you fixed. - Barracuda — Visit
http://www.barracudacentral.org/lookups, enter your IP, click "Request Removal." - SpamCop — Usually auto-expires within 24-48 hours after spam reports stop. No manual process.
Step 4: Monitor
After delisting, monitor your IP for re-listing:
- Set up daily blacklist checks via MXToolbox monitoring (free tier available).
- Review mail server logs weekly for anomalies.
- Monitor bounce rates and complaint rates from your ESP dashboard.
Prevention
- SPF, DKIM, DMARC — Properly configured email authentication reduces the chance of being flagged.
- Warm up new IPs — Start with low volume and gradually increase over 2-4 weeks.
- Monitor feedback loops — Register with ISP FBL programs (Gmail Postmaster, Yahoo CFL, Microsoft SNDS).
- Clean your lists — Remove hard bounces immediately and inactive subscribers after 6 months.