A Message-ID is a unique alpha-numeric identifier for Usenet posts.

If you have the Message-ID, it is relatively easy to find the post in question.

Every newsreader will have its own method for displaying the headers of Usenet posts. This tutorial demonstrates how to find the Message-ID using Agent and Advanced Google Group Search.

Agent is the newsreader that I use most often for participating in Usenet.

Google Groups Search page.