Email getting automatically unsubscribed

Hi there,
I have setup Mautic successfully and am able to send out emails as the workflow. The issue is that for one of the email addresses, the email gets automatically unsubscribed as soon as the email is received by the recipient.

Can you please advice is there is something I need to change at our end. Not sure how the unsubscribe link gets triggered though the recipient did not click the unsubscribe link.

Ravi