I've been wondering about this for a while and before I started doing some testing thought I'd check if anyone has already tried it out...
Seems to me you can have a mailing to a number of groups set up at least 3 different ways:
individual sub groups - eg members, online, others - with "Main" as the parent. In this scenario "Main" actually has no contacts of its own
in the actual mailing, just specify the 3 groups directly.
set up a smart group based on a search builder search of the contacts in the 3 groups
there may well be other ways.. My question is; when a recipient presses "unsubscribe" to a mailing, does the same outcome happen in each of the above scenarios?