Thanks for reaching out to the Emma Community! This is an interesting idea, but we don't have this in place currently. Depending on how your account is set up, contacts are opted out on a sub-by-sub basis, or by a universal (all subs) basis. Each individual sub can ask that their contacts manage their preferences in choosing which groups they prefer to hear from, but this is done in each individual sub, and there's nothing available at the top level. Do you have any questions about this? If so, give me a shout - I'm happy to help!