I'm reading https://community.constantcontact.com/t5/Developer-Support-ask-questions/WElcome-Email-Not-Sending/t... this topic.
Hello,
Thank you for reaching out to the API Support team here at Constant Contact.
When working with our current V2 API, the two options you have for action_by when submitting a contact are:
As long as your integration is for a contact signing themselves up, you can use ACTION_BY_VISITOR. If you are not, you may consider instead creating an Autoresponder email campaign that is sent to all contacts who are new to a list, regardless of how they are added.
Please let me know if you have any other questions!
Sincerely,
David B.
API Support Engineer