Test Campaign - Optout

Hello community,

I'm facing an issue which I'm wondering if someone can help. I'm running a test with a campaign that I created. When I click on the 'Send Test', the campaign is sent to the Target List, but for some reason, as soon as the email is sent. It's marked as 'Opt-out' without the user interacting with it. I checked the admin panel and I confirm that the option "Opt-out new email addresses by default" is unchecked.

Can someone please help?

Thanks