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API internal server error

Occasional Contributor

API internal server error

Hello API developers,


When I tried to upload our contact list through your API, I met a server error as shown in the picture below. I've noticed that the issue mostly happened when our list has over 400 contacts. Could you please tell me how to solve it?


API upload issue.jpg


Awaiting for your reply!




Tags (2)
Occasional Advisor

Re: API internal server error

I came here to report this same issue. I am getting the error on several lists but I got 2 of them to go through. One list had 544 contacts. I have a smaller list but it did not go through. I don't think it's related to size. My JSON data for the bulk upload shows no formatting issues either. Using the same JSON payload i also get the same error using the v3 developer portal. Hopefully someone from API support will respond soon as our integration is broken at this point.

Regular Visitor

Re: API internal server error

I face the same issue. 

Occasional Advisor

Re: API internal server error

Is anyone at Constant Contact aware of this issue? We are still getting the same error on some of our lists.


Re: API internal server error

Hi Everyone,


The cause of these errors are generally unique to each scenario. The are most likely caused by bad or invalid data. If there is no obvious data that can be located in your import that is causing a problem can you please email your data payload to us so we can look at each case individually. You can email us at webservices(at)constantcontact(dot)com.

Jimmy D.
Tier II API Support Engineer