[Mailman-Users] How to create a topic?

[Javad Hoseini-Nopendar]

Hello
I have created a mailing list named IranRAVI at IranRAVI.com, but I have a
problem. I believe a few members of the mailing list don't really like to
receive all the emails of the list. They don't like to take part in
discussions. but they only like to receive the newsletters. Now I want to
create a Topic or a sub-mailing list. For example:
IranRAVI-Newsletter at IranRAVI.com

This way, when I send an email to IranRAVI-Newsletter at IranRAVI.com, the
subscribers of this list will only receive the newsletter, but can't reply
to group. They can only reply to the sender. At the same time, the
subscribers of IranRAVI at IranRAVI.com will also receive this email. The
subscribers of IranRAVI at IranRAVI.com should be able to take part in the
discussions by replying to the group. I know the users can change the
reply-address manually, but that is not what I am looking for. Maybe this
matter refers to Umbrella list, but I really couldn't make heads or tails of
umbrella lists. Please explain to me clearly what I should do.

Thanks in advance.