Carl Fink wrote:
What I'd like to do is write a plugin. However, I have been unable to find a description of a Mailman plugin API
While I agree with the previous poster that Mailman may not be the tool you're looking for, the answer to your question is: The place in mailman to look is at the pipeline module. What it sounds to me that you are describing is a pipeline step that does much more customization to the message at fan-out time. Look at the VERP stuff...