"Resend to Non-Openers cannot be used on a campaign that has been resent to new contacts" Why not?

[CharlieZ1701]

On Friday, I sent a newsletter out to my existing list of recipients, but then identified additional contacts that needed to received it, and sent it to them. 

Now I would like to schedule a resend a few days from now, targeting those who did not open it the first time. Unfortunately, I got this message when attempting to schedule the resend:

Resend to Non-Openers cannot be used on a campaign that has been resent to new contacts.

I don't understand why this would be, other than a technical limitation - it's not like I'm trying to sneakily resend it to anyone who has already opened it. What is the difference between having sent it to everyone all at once, versus sending it to one batch initially and then to a second batch of recipients a short time later?

Regardless of the why - how do I resend this newsletter again to those who haven't opened it the first time?

[William_A]

Hello @CharlieZ1701 ,

Since the email has technically been re-sent with the selection of those new, additional contacts, it's now softlocked from scheduling for resend-to-non-openers. This is done as an anti-spam measure. Your best option now is to make a list from the Did Not Open drilldown, copy the email, then send the copied email to the new Did Not Open list.