<p>One thing to note is that if you add full SpamAssassin headers onto list messages this bulks up the messages significantly. These headers are also available to list subscribers, which might make it easier for someone malicious to work out how to evade your spam scanning strategy. I would suggest that Spam headers are not added for Mailman incoming mail, or minimal (short) headers added, or that they are stripped somewhere. However having minimal headers on means that you can, for example, moderate all messages which have a given spam rating (as well as bouncing messages with a very high rating).</p>
<p>One thing to note is that if you add full SpamAssassin headers onto list messages this bulks up the messages significantly. These headers are also available to list subscribers, which might make it easier for someone malicious to work out how to evade your spam scanning strategy. I would suggest that Spam headers are not added for Mailman incoming mail, or minimal (short) headers added, or that they are stripped somewhere. However having minimal headers on means that you can, for example, moderate all messages which have a given spam rating (as well as bouncing messages with a very high rating).</p>