Hello Andy2019,
Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
I'm sorry for the issue that you are experiencing with unsubscribed contacts receiving emails. This issue can be caused by a few different factors, none of which are related to Constant Contact's API, so I’m going to escalate this case to one of our Tier 2 support specialists so that they can follow up directly regarding this issue.
They should be in touch within 4 business days. Otherwise, for immediate assistance, or if you’d like a callback/email from them at a certain day/time you can call our support line at 866-289-2101 and reference case # 30713433.
Please have a look and let us know if you have any other questions!
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