Thank you for reaching out to the community!
We apologize for any trouble you are having with invalid sign-ups. I will explain what is happening here; the sign-ups that you are receiving are (in most cases) done by what is called a "bot." A bot is a program or computer that is filling out sign-up forms all over the internet at one time to try and collect information. When this happens the program is inputting an email address along with other required information following a standard format such as email@example.com. When this information is placed into the email portion of the form it is considered to be in the correct format, therefore, it will be added to your list. The Constant Contact system has no way to determine that a domain is valid or not.
Even though there is no way to prevent this from happening, we have a safety in place. When a sign-up form reaches 50 consecutive sign-ups in 24 hours it will place a CAPTCHA check on the form. This check will be able to prevent any additional sign-ups from being added by a bot. Only a human can fill out this CAPTCHA check due to its complexity. At this time the only way to have the CAPTCHA show on a sign-up form is by the process mentioned above.
I hope this helps!
Please let us know if there is anything else we can do for you.
It would be a great feature to allow your customers to add specific domains to block. There are sites that offer "burner" email addresses (just search for "burner email") that are commonly used for fake sign-ups.
Is there an official way to make these requests to Constant Contact? If enough customers make this request, would the company consider adding this feature?
I could absolutely see how that would be a very useful feature! Really, here or in a chat or a call work perfectly fine for passing along suggestions and we are always happy to receive more. I would be happy to pass that feedback along to the appropriate teams for review!