Can a member of a group decide they do not want any email from the main group but choose to get email from a subgroup?
Yes.
A member of a subgroup has a Subscription page for the subgroup which is separate from the one for the primary group (and separate from any other subgroups). They can choose whatever Email Delivery option they prefer for each.
From what I can see, if they unsubscribe from the main list, they are out of the entire group.
True.
They would need to remain members of the primary group. But, they can set their primary group Subscription to No Email or Special Notices Only.
Shal
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