Retrying a newsletter that initially failed to send does not reach new subscribers

I recently launched a new website and failed to send my first newsletter to 578 subscribers because Mailgun’s automated system flagged me. I have since cleared up the issue with Mailgun support and had my sending privileges restored, and in the mean time I gained a few hundred more subscribers.

When I returned to Ghost and tried to resend the newsletter, it worked… but it only reached the original 578 recipients, not the new subscribers I gained since the first failed attempt. Is there a way I can remedy this and send the newsletter out to all of my subscribers?