I've already submitted several support tickets on the main MailPoet website on this. I don't know if it's a language barrier or how else to explain it but somewhere along the line, the support person trying to help me doesn't seem to understand the issue, so I'm posting here.
Sometimes, subscribers either forget or don't click the link in their email to confirm their subscription. There is a feature inside MailPoet to manually confirm unconfirmed subscribers. When subscribers are manually confirmed, the emails that those people are registering for are NOT sending.
This is a big problem and needs to be fixed.