Hi @Palama,
Thanks for sharing some more about this!
You can always exclude users from your campaign sends through certain flow or list exclusions. If you don’t want those who bought in the last four days from the pre-sale, you can create a segment of those users with the condition: What some has or hasn’t done > Placed order > at least once > in last four days > over all time. This condition will dynamically group all users who fit this segment condition.
Do you have any active flows at the moment? Although you haven’t sent a campaign to your 3k mailing list recently, is there a chance that any of them have recently gone through a flow? It should be noted that Smart send includes flow messaging within their parameter of ‘message received by user’, not just campaign send.
With all that being said I would also lower your smart send to 16 hrs and see what that yields.
Hope this helps!
-Taylor