If your emails aren't reaching recipients, it could be because your server IP is on a blacklist. In this article, we explain what blacklists are, how to check if you're blocked, and how to get off a blacklist.

What is an email blacklist?

An email blacklist (also called blocklist or DNSBL) is a list of IP addresses suspected of sending spam or malware. Mail servers around the world use these lists to filter suspicious emails.

How does it work?

  1. You send an email
  2. The receiving mail server checks if your IP is on known blacklists
  3. If your IP is on a blacklist, your email is rejected or marked as spam

Why do you end up on a blacklist?

The most common causes:

  • Hacked email account - A compromised account sends spam
  • Infected computer/website - Malware sends emails without your knowledge
  • Poorly configured mail server - Missing SPF, DKIM or DMARC records
  • Open relay - A mail server that allows anyone to send mail
  • Bad sending practices - Too many emails in a short time, purchased mailing lists
  • Shared IP - Someone else on the same server IP is misbehaving
  • Spam complaints - Recipients mark your legitimate mail as spam

Checking your IP on blacklists

Step 1: Find your mail server IP

You need to know which IP address your mail server uses:

Via terminal (Mac/Linux):

nslookup -type=mx yourdomain.com

Via online tool: Go to MXToolbox.com and enter your domain.

Step 2: Check for blacklists

There are several free tools to check if your IP is on a blacklist:

MXToolbox Blacklist Check:

  1. Go to mxtoolbox.com/blacklists.aspx
  2. Enter your IP address or domain
  3. Click "Blacklist Check"
  4. The tool checks dozens of blacklists at once

MultiRBL.valli.org:

  1. Go to multirbl.valli.org
  2. Enter your IP
  3. View results from 200+ blacklists

Other popular tools:

  • Spamhaus Lookup: spamhaus.org/lookup
  • Barracuda: barracudacentral.org/lookups
  • SURBL: surbl.org

What to do if you're blocked

Step 1: Identify the cause

Before requesting delisting, you must find and fix the cause:

Check for compromised accounts:

  1. Log in to DirectAdmin
  2. Go to "Email Manager" > "Email Queue"
  3. Look for large amounts of outgoing mail in the queue
  4. Check which email account is sending the messages

Check your website for malware:

  1. Scan your website with tools like Sucuri SiteCheck
  2. Check for suspicious files or code
  3. Look in your server logs for suspicious activity

Check your DNS records:

  1. Do you have an SPF record?
  2. Is DKIM configured?
  3. Consider adding DMARC

Step 2: Fix the problem

Depending on the cause:

Compromised account:

  • Change the password immediately
  • Enable 2FA if possible
  • Check that no unknown forwarding rules are set

Infected website:

  • Remove the malware
  • Update all software (CMS, plugins, themes)
  • Change all passwords

DNS problems:

  • Add a correct SPF record
  • Configure DKIM signing
  • Implement DMARC

Step 3: Request delisting

Each blacklist has its own delisting procedure. Here are the most important ones:

Spamhaus:

  1. Go to spamhaus.org/lookup
  2. Enter your IP
  3. If you're listed, click on the listing
  4. Follow the instructions for delisting
  5. You must prove the problem is resolved

Spamcop:

  1. Go to spamcop.net
  2. Spamcop removes listings automatically after 24 hours without new complaints
  3. Fix the problem and wait

Barracuda:

  1. Go to barracudacentral.org/lookups
  2. Look up your IP
  3. Click "Request Removal"
  4. Fill out the form

SORBS:

  1. Go to sorbs.net
  2. Use their lookup tool
  3. Follow the delisting instructions (often a small fee)

Microsoft/Outlook.com:

  1. Go to sender.office.com
  2. Register your IP/domain
  3. Submit a delisting request

Prevention: Avoid future blacklisting

Best practices for email sending

Set up authentication correctly:

  • SPF: Specify which servers may send mail on your behalf
  • DKIM: Digital signature for your emails
  • DMARC: Policy for how recipients should handle failed authentication

Healthy sending practices:

  • Only send to people who have opted in
  • Process unsubscribes within 10 days
  • Keep your bounce rate under 2%
  • Keep spam complaints under 0.1%

Technical measures:

  • Use strong passwords for all email accounts
  • Enable 2FA where possible
  • Limit the number of emails per hour/day
  • Monitor your outgoing mail queue

Check regularly

Set a reminder to check your IP for blacklists monthly. This way you discover problems before they have a big impact.

Frequently asked questions

"How long does delisting take?"

This varies by blacklist:

  • Some are automatic within 24-48 hours after fixing the problem
  • Others require manual review and can take 1-7 days
  • Spamhaus can take up to 2 weeks in serious cases

"I'm on a blacklist but I'm not sending spam"

This could be due to:

  • Another user on the same shared IP
  • A hacked account without your knowledge
  • Your IP was previously misused by someone else

"Do I need to address all blacklists?"

Focus on the most important ones:

  1. Spamhaus - Most influential
  2. Barracuda - Many business users
  3. Microsoft - For Outlook.com/Hotmail recipients
  4. Google - For Gmail recipients

Smaller blacklists often have less impact.

"Can I get a new IP?"

Sometimes this is an option, but:

  • It doesn't solve the underlying problem
  • The new IP may also have a bad reputation
  • It's better to fix the problem

Monitoring and prevention tools

Free monitoring

  • Google Postmaster Tools: Insight into your reputation with Gmail
  • Microsoft SNDS: Smart Network Data Services for Outlook
  • MXToolbox Monitor: Free monitoring of your domain
  • SendGrid: Email delivery service with built-in reputation management
  • 250ok: Comprehensive email deliverability monitoring
  • GlockApps: Test inbox placement and blacklist monitoring

Need help?

We're here for you! Running into issues or have questions? Our support team is happy to help you personally. Drop us a message through the ticket system - we usually respond within a few hours and love helping you find the best solution.