The firstname.lastname@example.org mailing list is for discussing newlib, asking questions, reporting bugs. It is a low-volume mailing list.
GIT commit messages are automatically sent to email@example.com (pardon the historical name of the mailing list) so that people can see changes. Don't send messages to this list, it's automated.
There is also the firstname.lastname@example.org mailing list for discussing embedded development with the GNU tools.
Just click the above links to subscribe to, or unsubscribe from the respective mailing list. The same links allow access to the web archives, too, if you'd like to browse the list discussions.