Spamhaus / SpamCop Filtering

Some senders may receive notifications stating their emails were refused due to blacklisting on Spamhaus or SpamCop. This guide explains why this happens and how to resolve it.

What are Spamhaus and SpamCop?

Spamhaus and SpamCop are DNS-based Blackhole Lists (DNSBLs) that maintain registries of IP addresses flagged as spam sources. These services are widely used by email providers to filter incoming mail.

ImprovMX screens incoming messages against both lists to:

• Maintain a good quality of service
• Protect our sender reputation
• Prevent spam from affecting all users on our platform

What ImprovMX Tests

For every incoming email, ImprovMX validates three data points:

1. The sender's connecting IP address - The actual IP making the SMTP connection
2. The sender's domain IP address - The IP associated with the domain in the sender's email (e.g., test.com from hi@test.com)
3. The recipient's domain IP address - The IP associated with your domain

Error Messages

Depending on what triggered the block, you may receive one of these error messages:

Sender IP Blocked

571 Your IP is blacklisted on Spamhaus. See https://www.spamhaus.org for details.
571 Your IP is blacklisted on SpamCop. See https://www.spamcop.net for details.

Domain IP Blocked

571 The IP from the domain 'example.com' is listed on Spamhaus.
571 The IP from the domain 'example.com' is listed on SpamCop.

How to Get Delisted

If you believe the listing is incorrect, you can request removal through the respective service's delisting portal:

Service	Delisting URL
Spamhaus	spamhaus.org/lookup/ - Use the lookup tool to check your status and request removal
SpamCop	spamcop.net/bl.shtml - Access the blacklist lookup system for delisting requests

Note: Both services provide mechanisms to contest blacklist listings. If your IP was listed due to a compromised server or temporary spam issue that has been resolved, delisting is usually straightforward.