I have a list of unsubscribers from another service I was using. Some people accidentally were placed on the list and some purposely unsubscribed. Am I allowed to upload this list and send from Marketo since it's another service or since these people already unsubscribed, I cannot reach out to them again?
I would recommend not contacting them again. In my eyes, even though you've switched services, you still work for the same company and should honor the request to not be contacted.
I feel your pain, I really do, but it's a line I would suggest you stay very far away from crossing. If it's not that difficult, it would be worth taking those people out of the list who were accidentally placed there though.