Scenario: New leads are being added into a Salesforce.com instance, and as a result are being injected into a Marketing Cloud Journey Interaction. These are always new leads, unknown in the Marketing Cloud instance.
Problem: Since these are new subscribers, they won't be in the All Subscribers list. In the old system, I would have just marked this Data Extension as Root, and added the email address to the Channel Address Order. This system has been replaced with Populations.
With Populations, I am not seeing the ability to use the resulting Salesforce Journey Data Extension as the base. Meaning I can't use this Data Extension which is really the only source I need for new subscribers. So with the subscribers not being in the All Subscribers list and this Data Extension not marked as root, subscribers are failing on the first email interaction.
I feel as though this is a somewhat common use-case being describing, so I am hoping I am just missing something obvious with this new system. Does anybody have the way around this?
BONUS: If a Lead converts to a Contact midway through a Journey, will emails still be sent to the Lead instance of their subscriber?