Simple subscriber list application for a boy scout troop

I need to set up a simple subscriber list application for our boy scout troop. When a subscriber (member of the troop) sends a message to the troop (for example the email will be then forward to all subscribers. If someone then replies to the email it will, in turn, be forward to all subscribers ect…

I was told by InMotion support that I could set this up in phpList. Can this be accomplished with phpList, if so could anyone point me in the right direction? If not, can you suggest another application?

No, this is not what phpList is designed to do. You have setup a list server, which provides ‘many to many’ email communications.

phpList provides ‘one to many’ communications. Where one email is sent to many subscribers. Responses are sent only to the ‘replyto:’ email address, not all of the subscribers.

What you describe sed to be possible using Yahoo Groups, sadly this is no longer really viable.
Have a look at this site which describes the alternatives available now.