Order Notification Emails Not Sending

For some reason our order notification emails don’t always get sent. Only about 75% of our customers get sent the order notification email. I’ve gone through each customer and can’t figure out why it isn’t always getting sent out. There doesn’t seem to be any pattern to those who have received it and those who haven’t been sent it.

We also have a follow up product email running and it seems to be working fine. Is there something we are missing?

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