A group Tree mail
can be a good thing but only if each person understands ahead of time and has made the decision to be part of the group mail.
If you send a group Tree-mail out to 10 people and each person responds...it will trigger a notice of new Tree mail to each and every person each and every time....whew

...that's a lot of red envelopes. Please, before you send out the group mail, ask each person individually if they understand what being part of a group Tree- mail involves.