Why doesn't the Horde Blacklist feature always work?
There are multiple different variations of the "From Address" in an email in the form of email headers:
- envelope-from - (Part of the Recieved header)
If you'd like to review the email headers for one of your messages, you can use the following resource to find them:
It is possible for a sender to avoid getting caught by the Horde blacklist if they manually set the From header to a different value from what is found in the envelope-from portion of the Recieved header.
You could try to resolve this by checking the headers of the message and blacklisting the envelope-from address. Although this could create further problems if the message is from a reputable sender such as Constant Contact. If you block a generic email address such as one from Constant Contact, you may end up losing emails that you actually want to receive from other companies that are making use of the email service.
A better solution in those situations is to unsubscribe from the message by using the unsubscribe button inside of the message. Reputable senders such as constant contact will respect this action.