How do I search for all unsubscribed e-mails across any/all groups
Not sure what version of Civi you are on (I'm on 4.7.9), but take a looking under Reports > Mailing Reports > Mailing Detail Report - I think this will give you a good solid list to work with (see attached screen shot for available columns) - on the filters tab you also have the option to filter by group.



Hope this helps!
Tamar