Google has an old but still working product called “Google Groups”. For most users it behaves like a 1980’s  email list, but there’s also a web interface.
One advantage of Google Groups/Email list is that it works with … email. You can send emails out and everyone gets it (in theory). The problem with Groups is the modern email problem — many times email is lost, blocked as spam, filtered out, bounces etc.
Another advantage is that you don’t need to give away too much personal information. You don’t even need a Google Plus account. It will work with non-Google email, though I think it does require some kind of Google setup. Google Group/email is more privacy friendly than most of our current communication options.
There’s a web archive of past messages and conversations that’s password protected.
You can view the archive and accept invitations here:
I believe you can also go to that URL and request an invitation — useful if you wish to add a new email address or if you didn’t get an invite (probably filtered out by spam filter). It does work best with Google email of course.
As old folks know, group communication was probably easiest in 1994! Things are rather more challenging now.
 For most of our riders that’s so long ago it blurs into World War II.
PS. If you’re a super-duper geek there’s actually a no-longer documented way to follow Group activity with RSS feeds, but I don’t know if it works with private groups like ours.