Some emails are refused because of Spamhaus or SpamCop, why?

You might have received a notification from some of your senders saying that their email was refused by ImprovMX because their domain or IP addresses are listed on Spamhaus or SpamCop.

Spamhaus and SpamCop are what we call DNSBL (Domain Name System-based Blackhole Lists). They have a list of IPs addresses that are identified as Spammers.

We check every incoming email we receive against Spamhaus and SpamCop to verify that the sender is not blacklisted. When they are, we refuse the email in order to not lower our sender reputation and maintain a good quality of service for everybody else.

We test the following data when an email is forwarded via ImprovMX:

1. The IP of the client that connects to ImprovMX
2. The IP of the domain associated with the sender (test.com when the sender is hi@test.com for instance)
3. The IP of the domain associated with the recipient

We display a different message based on the data tested:

For 1, we display one of the following messages:

571 Your IP is blacklisted on Spamhaus. To best protect our users from spam, we will ignore all incoming emails from you until the matter is resolved.

571 Your IP is blacklisted on SpamCop. To best protect our users from spam, we will ignore all incoming emails from you until the matter is resolved.

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For 2 and 3, we display one of the following messages:

571 The IP from the domain “example.com” is listed on Spamhaus. To best protect our users from spam, the message has been blocked.

571 The IP from the domain “example.com” is listed on SpamCop. To best protect our users from spam, the message has been blocked.

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If you believe that Spamhaus blacklisted your IP address or domains by mistake, you can request removal at Spamhaus by following this link.

You can carry out the same process for SpamCop by following this link.