The Relief_Society-L list is managed by topica.com.
To get to the topica site, type: http://www.topica.com.
When you have accessed the main page, register as a user by clicking on the "sign up - it's free" icon. Once you have done this, do a search for the email list titled: "relief_society-l".
You will see a list of email list names -
click on the "relief_society-l" list. That will bring you to a description
page which gives a brief introduction to the list. At the very bottom
of this page, there is a button which says "join this list". Click
on that to subscribe to the list.