MailPoet 3 not sending Newsletter nor welcome emails.

Hello, I’m trying to set up some E-mail to send with MailPoet for Subscribers to my newsletter. My website is not yet published yet but I can’t get automatic mail to work. My account has been approved and verified but after filling in the form to subscribe to the newsletter I get an error saying:

“MailPoet 3 Subscriber added to lists, but confirmation email failed to send.”

All I receive is a mail that contains just a text that says: “On On”.
I already have created the templates for the welcome, post notification and newsletter mail but we can’t receive them. One of my colleagues has tried subscribing but instead of the “On On” message he received the default MailPoet welcome mail.

Help us please!!!

The page I need help with: [log in to see the link]