@ryanhungate I had this exact same issue, and this is great advice, but my situation would require me to write 30k+ user meta entries, which I’d rather avoid if possible.
Would it be possible to “export” the audience that was sync’d via the plugin from Mailchimp.com, delete those contacts, then re-import them as “subscribed”? I included a unique subscriber tag during the initial sync, so targeting those folks on Mailchimp.com is easy. Additionally, I now have to plugin properly setup, and it’s working great, so this would be a “one time” action. I’m not entirely sure how the plugin tracks what has/hasn’t been synced though, so my fear is that doing this will simply re-trigger some massive sync that ends up overriding all the newly imported “subscribers” anyway.
Any advice to subscribe a large number of folks flagged as “transactional” without making massive database changes would be much appreciated. Cheers!