Overview

You want to configure your LM instance to autoreply to unsubscribe requests when the email address is already unsubscribed or not on the list. Alternatively, you want an automated message to go out to anyone who posts to a list but is not a member of the list, or when there is an error.

Solution

LM (Versions 10.2d and above) does not send rejection messages to senders when their email messages are rejected. Typically, rejection messages are sent for one of the following two reasons:

• The sender is not a member of the list - They have already unsubscribed or they were never a member
• A message is too large

These rejection messages are suppressed in order to prevent Backscatter spam attacks. Backscatter can occur when List Manager sends rejection messages to forged sender addresses. As a result, malicious senders are able to send spam using ListManager as a relay.

1. Browse to Utilities > Administration > Server > Server Settings > Security
   
   
2. Select the Spam Blocking tab
   
   
3. In the Error Responses section set Suppress error response to No
   
   
4. Stop and restart the ListManager services.

The server will now send rejection notifications, such as the following:

Sorry your message was not sent out to [listname] because it is too large. 
The maximum message size is [max size] and your message was [message size] 
long.

or

Member 'USER_NAME@DOMAIN.COM' is already unsubscribed so ignoring this request.

Where USERNAME@DOMAIN.COM is the address of the person who unsubscribed.

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