It sounds like you are referring to the Sign-up & Unsubscribe Update emails customers have the option to receive. I'm sorry to hear you are receiving notice that bad email addresses are signing up for your email campaigns. The email notifications just pull the information from your contact management area as the contacts arrive or unsubscribe. It is not able to distinguish between legitimate contacts and fake contacts.
We would want to be able to see the source of where the bogus contacts are coming from. If they are appearing in the email notification then they are being added through a sign-up form on your website or social media page. If you could confirm that for us it would help us narrow down our investigation.
The next time you notice bogus contacts appear please reach out to us at social_support(at)constantcontact(dot)com with your username, the contacts in question, and a reference to this post and that will give us some examples to work with. I ask that you do not delete them before we look at them because when contacts get deleted we lose the source of where they were added from.
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