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.
It looks like we reached out to you via email regarding this issue to request some additional information in order to better assist with troubleshooting. If you still need assistance with this, please let us know! If you haven't received our reply, please let us know via email at email@example.com, and reference case number 31052428.
For a full list of Constant Contact’s IP addresses and URLs, I am also including a detailed support article below.
Safelist Constant Contact web domains in a security program:
Please have a look and let us know if you have any other questions!
View API documentation, code samples, get your API key.Visit Page
Join our list to be notified of new features and updates to our V3 API.Sign Up