When you schedule the batch campaign, in the smart campaign settings, ensure you choose:
As mentioned above, this is a setting in the schedule tab. Select edit and choose:
1) flow through once
2) Flow once every x days
3) flow every time
depending on your requirements
You can setup comm limits. Other way is rather to consider the leads as "member of list" where you're adding the leads, you can use the trigger "added to list" with a filter "not sent email" and adjust the flow with a wait step if required.