When MXToolbox flags your server IP on the ivmSIP/24 blacklist, it typically indicates suspicious SMTP activity. This spam trap list focuses on /24 IP blocks (Class C networks) exhibiting patterns like:

• Unexpected SMTP connections from non-mailserver IPs
• Spam-like behavior from any IP in the network range
• Missing or misconfigured reverse DNS (PTR records)

First, confirm your exact blacklisting status using these Linux commands:

# Check if your IP appears in ivmSIP/24
dig +short your.server.ip.ivmSIP.bl.blocklist.de

# Verify SMTP configuration
telnet your.server.ip 25
EHLO yourdomain.com

1. PTR Record Validation
Ensure your reverse DNS matches your SMTP banner:

# Example BIND zone configuration for PTR
$ORIGIN 1.0.10.in-addr.arpa.
123     IN      PTR     mail.yourdomain.com.

2. SMTP Hardening
Implement these Postfix main.cf settings:

smtpd_banner = $myhostname ESMTP $mail_name
smtpd_helo_required = yes
smtpd_helo_restrictions = 
    permit_mynetworks,
    reject_invalid_helo_hostname,
    reject_non_fqdn_helo_hostname,
    reject_unknown_helo_hostname

The ivmSIP/24 list automatically removes IPs after 24-48 hours of clean behavior. For urgent cases:

1. Prepare evidence of your fixes (screenshots of DNS records, SMTP logs)
2. Send delisting request to abuse@blocklist.de with subject: "Delist Request for [IP]"
3. Include relevant technical details:

Server IP: 192.0.2.123
PTR Record: mail.example.com (verified)
SPF Record: "v=spf1 ip4:192.0.2.123 -all"
SMTP Log Excerpt: [paste sanitized log showing clean connections]

Implement ongoing monitoring with this Python script:

import dns.resolver, smtplib

def check_blacklist(ip):
    bls = ['ivmSIP.bl.blocklist.de']
    listed = []
    for bl in bls:
        try:
            dns.resolver.query(f'{ip}.{bl}', 'A')
            listed.append(bl)
        except:
            pass
    return listed

def test_smtp(ip):
    try:
        with smtplib.SMTP(ip, 25, timeout=10) as s:
            s.ehlo('test.example.com')
            print(s.docmd('NOOP'))
        return True
    except Exception as e:
        print(f"SMTP test failed: {str(e)}")
        return False

When your server IP appears on the ivmSIP/24 blacklist, it typically indicates that your IP address has been flagged for sending suspicious or unsolicited emails. This can severely impact your email deliverability. The blacklist specifically targets /24 IP blocks (Class C networks), meaning entire ranges can be affected.

Before taking action, confirm your blacklist status using multiple tools:

# Python script to check multiple blacklists
import dns.resolver

def check_blacklist(ip, blacklist):
    query = f"{'.'.join(reversed(ip.split('.')))}.{blacklist}"
    try:
        answers = dns.resolver.resolve(query, 'A')
        return "LISTED"
    except:
        return "NOT LISTED"

ip_address = "your.server.ip.here"
blacklists = ["ivmSIP.ironport.com", "bl.spamcop.net", "zen.spamhaus.org"]

for bl in blacklists:
    print(f"{bl}: {check_blacklist(ip_address, bl)}")

• Outbound spam from compromised accounts
• Open mail relay configuration
• Missing or incorrect SPF/DKIM/DMARC records
• High bounce rates from your mail server
• Historical reputation issues with the IP range

1. Check your mail server logs for suspicious activity:

# Linux command to check recent outbound mail
grep 'sending' /var/log/mail.log | tail -n 100

2. Update your SPF record to explicitly include your IP:

# Example SPF record for DNS
v=spf1 ip4:192.0.2.1 ip4:192.0.2.2 include:_spf.yourdomain.com -all

3. Implement DKIM signing for all outgoing emails.

To request delisting:

1. Visit the Cisco Talos Intelligence website (ivmSIP is part of Cisco's IronPort)
2. Submit a delisting request through their portal
3. Provide details about remediation steps taken
4. Include evidence of fixed issues (screenshots of updated DNS records, etc.)

Implement these technical safeguards:

# Postfix configuration example to prevent open relay
smtpd_recipient_restrictions =
    permit_mynetworks,
    reject_unauth_destination,
    reject_unknown_sender_domain,
    reject_unknown_recipient_domain

Regularly monitor your mail server reputation using tools like:

• MXToolBox SuperTool
• SenderScore by Return Path
• Google Postmaster Tools

Consider setting up automated blacklist monitoring:

# Python script for automated blacklist monitoring
import smtplib
from datetime import datetime

def check_and_alert():
    if check_blacklist(ip_address, "ivmSIP.ironport.com") == "LISTED":
        send_alert_email()

def send_alert_email():
    server = smtplib.SMTP('smtp.yourdomain.com', 587)
    server.starttls()
    server.login("your@email.com", "password")
    msg = "Subject: Blacklist Alert\n\nYour IP has been blacklisted."
    server.sendmail("your@email.com", "admin@yourdomain.com", msg)
    server.quit()