Thank you for bringing this to our attention! We have seen contacts receive duplicate emails in some cases where the same contact exists on multiple lists and the same email has been sent to these lists separately. Or even if the contact is set up distribution lists. Some companies have contacts on a distribution list so that sending to one email will also reach other addresses all at once.
With that being said, we definitely would like to troubleshoot this further for you. In fact, what are the contacts you are experiencing this with? Are theses contacts on multiple lists? Is the email address on a distribution list? Or even how are these contacts viewing the email (desktop, mobile device, etc.)? Please email these details to social_support(at)constantcontact(dot)com with your username and a reference to this post.
Thank you for sharing these details with us! Please email us your username, the contact that received these duplicate emails, the name of the campaign sent to them, and how they viewing the email (desktop, mobile device, etc.). You can send these details to social_support(at)constantcontact(dot)com with a reference of this post. Once we receive this email we can look into this further.