integration with other products

0 Votes

Very frustrating to me that if someone is already on another list, they don't get added to a new list through my various app integrations.  Kind of defeats the purpose because if someone is in my funnel and they finally become a member, or register for something, they don't get added to my list (i.e. through moonclerk and brilliant directories) so I have to do it manually. Also, I was told this was fixed and it wasn't.  Does anyone have any work arounds???

0 Votes

Hello TraceyM19,


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 apologize for any misunderstanding or inconvenience you've experienced regarding the functionality of the 3rd party integrations that you've connected with your Constant Contact account, I know it can be frustrating when a tool or service does not work as expected.


Constant Contact provides developers with free access to our API endpoints for developers building their own applications for integration. The actual coding and programming of the 3rd party integrations are not built or supported by Constant Contact, so we are limited in the support we can provide, but will try to answer any questions to the best of our ability as they pertain to Constant Contact’s API endpoints and functionality. 


After looking in our logs, I noticed that some of the 3rd party integrations connected to your account were returning 409 responses, which occurs when making a POST call to the /contacts endpoint for an existing contact, which can only add new contacts whose email addresses have not previously been added to the account.


API Response Codes


The developer of the integration should have their program check to see if an email address exists in the account, and then either create the contact or update the contact (as is shown in the flow below). However, some developers only code their integrations to create new contacts and do not not account for updating existing contacts. This can only be fixed by the developer of that 3rd party integration and is not something that Constant Contact can access or modify.


Step 1: Check to see if the contact exists in the account using the email address.
GET Contacts Collection!/Contacts/getContacts
Step 2: If the contact comes back as non-existent, use POST to create the contact:
POST (create) a Contact!/Contacts/createContact
Step 3: If the contact comes back as already existing in the account, use PUT to update the contact.
PUT (update) a Contact!/Contacts/putContact


Additionally, it looks like the 3rd party integration "MoonClerk" that you mentioned was disabled in 2021, as it was utilizing endpoints on our deprecated/retired V1 API. All integrations that utilize retired V1 API keys or endpoints are in the process of being fully deprecated & shut down, after which the V1 endpoints being used by the application will be turned off as well. You can contact MoonClerk directly for information on whether they offer an updated version of their integration at by clicking the chat bubble in the bottom right of their website. 


Hopefully that helps clear some things up. If you have further questions about the information above, please feel free to reach out to our team by email at and reference case #30079931.


Please have a look and let us know if you have any other questions!



Courtney E.
Tier II API Support Engineer

Did I answer your question?
If so, please mark my post as an "Accepted Solution" by clicking the Accept as Solution button in the bottom right hand corner of this post.
Developer Portal

View API documentation, code samples, get your API key.

Visit Page


API Updates

Join our list to be notified of new features and updates to our V3 API.

Sign Up