The message can be seen by each person. Yahoo Groups
(YG) has 3 kinds of subscriptions:
nomail -- people access from the web
digest -- people get a set of emails in their mail box
individual -- subscribers see each message.
Everyone can respond though if the list has them on
"moderation" for some reason, one of the moderators has to
approve it before it goes through.
YG also has the capability of file storage -- e.g., we have a set of
Meteonorm weather files here
links -- there are some Energyplus related links.
and from time to time we have polls.