A thread from today's hangout was about how to unsubscribe both one-time fraudsters and donors who donated to Wikipedia by mistake, the common thread being CIDs with only one donation ever, which became either a refund or a chargeback. TY @krobinson for the idea!

@Ejegg mentioned that there is a lot of filtering on the Silverpop side, so plenty of CIDs that are not marked No Bulk Emails (User Opt Out) will not receive fundraising emails. @mepps suggested looking into whether anything could be done in Civi to enable users to know more about which of these CIDs will not receive fundraising emails. It would make the use of the known fraudster checkbox much easier, and might reduce manual unsubscribing.