Adding a new, large opt-out list

I depends. If 19k isn't a lot compared to your whole DB size it probably won't matter, and you may just be able to work around it with your rep.

However, we do have a feature, durable unsubscribe that stores unsubscribes even if an email is deleted. You should test it out, but I think you could load your list and then delete them all, and you'd be safe moving forward.

How about just adding various Opt Out and "Cleaned" lists from other email platforms when migrating to Marketo? What is the best way to do this? We are migrating from MailChimp. Should I add those lists to the Unsubscribed Leads? Marketing Suspended? 

Thanks! 

Great question Lydia. We are in the process of moving from Silverpop at the moment and I will be moving over a 50k+ list of unsubscribes. I was just going to add them into the unsubscribed leads, but if there is a more efficient place to store them.... I'm all ears. In addition, we will finally be able to build out a true subscription management option for folks... So does anyone know if it would cause any issues by having all of these current unsubscribes in the Unsubscribed Leads, but then try and reengage them (I'm assuming with an operational email)?

Thanks Justin, 

I am having difficulty finding best practices for migrating to Marketo from another platform. It seems like this would be a common issue. Let me know if you find other resources!