The tlhIngan-Hol email discussion forum has been in existence since even before the KLI itself was formed in 1992, and over the years has been the site of many healthy debates and interchanges. It is an excellent learning tool for students of all levels. There are always new students beginning, and even some more advanced speakers actually conversing entirely in Klingon, all interacting.
To subscribe to the forum, just go to the list's online form page and follow the directions there.
This archive covers mail from 1993 until June of 2016. At that time the list was migrated to a new server and a new archive was created.