I got this manual https://elasticemail.com/api-documentation/send
Tried to call web-service using a dictionary for header:
Content-Type: application/json; odata=verbose
and a dictionary "postRequest" for request content (username, api_key, etc.) which I placed as a "request" at workflow. The call to web-service not working as I did not getting any e-mail. Also, I cannot read it's response. The source code from site on C# works just fine. I think I must use Fiddler to see which headers the program use. Maybe I'm doing something wrong.