The MML is a Mailman-hosted email listserv. In plain English, that means that the messages are sent to your inbox via email. You can then use your email program’s filters to sort the messages and discard messages you don’t want to see.
Joining the MML can be done by visiting https://list.moparmailinglist.com/mailman3/lists/mml.list.moparmailinglist.com/ and entering your email address, and optionally your real name.
You can optionally create an account with the sign-up link at the top of the page. This will enable you to see the member roster, as well as an archive of all previous MML posts, so it is highly recommended you do so.